AP Calculus BC · ClipSAT

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AP Calculus BC

Board · College Board Units · 1–10 (AB + 9–10) Exam · MCQ + FRQ, scored 1–5 Status · Preview
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Overview & units

🗺 AP Calculus BC — Additional Topics Beyond AB

UnitTitleExam %Key Topics
BC-1Advanced Integration17–20% (shared)Integration by parts, partial fractions, improper integrals
BC-2Logistic & Euler's Method6–12% (shared)Logistic growth model, Euler's method for DE approximation
BC-3Parametric & Vectors11–12% BC-onlyParametric derivatives, arc length, vector-valued functions
BC-4Polar Coordinates5–6% BC-onlyPolar graphs, polar area, intersections
BC-5Sequences & Series17–18% BC-onlyConvergence tests (integral, comparison, ratio, alternating)
BC-6Power, Taylor & Maclaurin17–18% BC-onlyTaylor/Maclaurin series, radius & interval of convergence, error bound

How to use this track

BC contains everything in AP Calculus AB plus the additional topics below — advanced integration, logistic models and Euler's method, parametric, polar and vector functions, and the full theory of sequences and series. The six BC chapters, worked free-response questions, and a 50-question practice exam are all here.

AP Calculus BC is a superset of AB. It shares Units 1–8 and adds:

Units 1–8
Everything in AP Calculus AB
Unit 9
Parametric, polar & vector-valued functions
Unit 10
Infinite sequences & series

The exam format matches AB (multiple choice 50%, free response 50%), and a BC result also reports an AB subscore.

⏱️ AP Calculus BC Exam Breakdown & Timing Strategy

  • Section I: Multiple Choice (50% of score, 45 questions, 105 min):
    • Part A (60 min, 30 questions, NO calculator): ~27 AB questions + ~3 BC questions. Pacing: 2 min/question.
    • Part B (45 min, 15 questions, Graphing calculator required): ~9 AB questions + ~6 BC questions. Pacing: 3 min/question.
  • Section II: Free Response (50% of score, 6 questions, 90 min):
    • Part A (30 min, 2 questions, Graphing calculator required): Typically Question 1 (Rate in/out or area/volume) and Question 2 (Parametric/vector motion).
    • Part B (60 min, 4 questions, NO calculator): Questions 3–5 cover differential equations/Euler, FTC graph analysis, and polar area; Question 6 is always Taylor Series & Error Bounds.
  • BC Scoring Thresholds: A composite score of roughly 62–66% earns a 5 on AP Calculus BC, and ~50–55% earns a 4. High performance on core AB topics combined with harvesting method points on Taylor series guarantees top scores.

💡 The Two Giant BC-Exclusive Capstone Pillars
  • Unit 9: Parametric, Polar & Vector Calculus (11–12% of exam):
    Extends single-variable calculus to curves in the plane: parametric slope dy/dtdx/dt \frac{dy/dt}{dx/dt} , second derivative (dy/dx)′dx/dt \frac{(dy/dx)'}{dx/dt} , vector velocity v⃗(t)=⟨x′,y′⟩ \vec{v}(t) = \langle x', y' \rangle , scalar speed ∥v⃗∥=(x′)2+(y′)2 \|\vec{v}\| = \sqrt{(x')^2+(y')^2} , arc length, and polar area 12∫r2 dθ \frac{1}{2}\int r^2\,d\theta .
  • Unit 10: Infinite Sequences & Series (17–18% of exam):
    The most challenging unit on the exam: convergence tests (Geometric, p-Series, Ratio, Limit Comparison, Alternating Series), absolute vs. conditional convergence, power series intervals of convergence, Taylor and Maclaurin polynomial constructions, and error bounding (Alternating Series Error vs. Lagrange Error Bound).
Bar chart: AP Calculus BC Topic Distribution (%) with categories: AB: Limits & Derivs (25), AB: Integration & FTC (20), BC-1: Adv Integration (18), BC-2: Euler & Logistic (9), BC-3 & 4: Param/Polar (12), BC-5 & 6: Series (18)06131925AB: Limits & Derivs25AB: Integration & FTC20BC-1: Adv Integration18BC-2: Euler & Logistic9BC-3 & 4: Param/Polar12BC-5 & 6: Series18Approximate Exam Weighting (%)AP Calculus BC Topic Distribution (%)
AP Calculus BC exam topic distribution across primary units and AB/BC split. Core AB topics account for ~60% of the composite score (and the AB Subscore), while BC-exclusive topics (Integration techniques, Euler/Logistic, Parametric/Polar/Vector, and Infinite Series) comprise the remaining ~40%.
Section I of AP Calculus BC consists of 45 Multiple Choice questions (Part A: 30 non-calculator questions in 60 minutes; Part B: 15 calculator-active questions in 45 minutes). Calculate the average time allocated per question for Part A versus Part B in minutes.
For Part A: 60 minutes30 questions=2.0 minutes per question\frac{60\text{ minutes}}{30\text{ questions}} = 2.0\text{ minutes per question}. For Part B: 45 minutes15 questions=3.0 minutes per question\frac{45\text{ minutes}}{15\text{ questions}} = 3.0\text{ minutes per question}. Part B grants 50% more time per question because graphing calculator input and multi-step interpretation are required.
📝 Chapter Quiz
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Beyond AB

▲ Parametric & polar

For a parametric curve, dydx=dy/dtdx/dt \dfrac{dy}{dx}=\dfrac{dy/dt}{dx/dt} . Polar area is A=12∫αβr2 dθ. \displaystyle A=\tfrac12\int_\alpha^\beta r^2\,d\theta.

▲ Series convergence

The ratio test: ∑an \sum a_n converges absolutely if lim⁡n→∞∣an+1an∣<1 \displaystyle\lim_{n\to\infty}\Big|\dfrac{a_{n+1}}{a_n}\Big|<1 . Taylor series and their intervals of convergence are the centrepiece of Unit 10.

▲ BC-only topics

AP Calculus BC extends AB with additional integration techniques, convergence tests, parametric/polar calculus, and infinite series — approximately 40% of the exam is BC-exclusive material.

BC-only: Series
Taylor/Maclaurin, ratio test, alternating series, error bounds
BC-only: Parametric
Slope dy/dtdx/dt \frac{dy/dt}{dx/dt} , arc length, speed =(x′)2+(y′)2 =\sqrt{(x')^2+(y')^2}
BC-only: Polar
Area 12∫r2 dθ \frac{1}{2}\int r^2\,d\theta , arc length, slope in polar
BC-only: Techniques
Integration by parts, partial fractions, improper integrals, Euler's method
🎯 The AB Subscore & Strategic Scoring in BC

  • Two Scores from One Exam: Every student taking AP Calculus BC receives both an overall BC Exam Score (1–5) and an AB Subscore (1–5) based solely on the ~60% of the exam covering AB topics (Units 1–8).
  • The College Credit Safety Net: Most colleges award Calculus I credit for an AB Subscore of 4 or 5, even if your composite BC score is lower. Mastering core AB calculus provides an unbeatable foundation for both scores.
  • Predictable BC FRQ Real Estate: The 6 Free Response questions always dedicate exactly 2 questions to BC-only material: typically FRQ 2 or 5 on Parametric/Vector Motion or Polar Area, and FRQ 6 on Taylor Series and Error Bounds.

⚠️ The Top 3 BC-Exclusive Scoring Traps
  • 1. Parametric Second Derivative: Differentiate dydx \frac{dy}{dx} with respect to t t , then divide by dxdt \frac{dx}{dt} . Never divide second derivatives directly: d2ydx2≠y′′(t)x′′(t) \frac{d^2y}{dx^2} \neq \frac{y''(t)}{x''(t)} .
  • 2. Lagrange vs. Alternating Error Bound: If an FRQ explicitly requires the Lagrange Error Bound, quoting the alternating series test bound (first omitted term) receives zero credit for the error bound point.
  • 3. Evaluating Limits for Improper Integrals: On Section II, you must write lim⁡b→∞∫ab \lim_{b\to\infty}\int_a^b rather than plugging in ∞ \infty as an endpoint.
Maclaurin Polynomials Approximating f(x) = eˣ — Coordinate plane with graph of f(x) = eˣ, P₁(x) = 1 + x, P₂(x) = 1 + x + x²/2; marked points (0, 1) Center (0, 1)-1124xyf(x) = eˣP₁(x) = 1 + xP₂(x) = 1 + x + x²/2(0, 1) Centery = 0
Taylor polynomial approximations to f(x)=ex f(x) = e^x centered at x=0 x = 0 . As the polynomial degree increases from P1(x)=1+x P_1(x) = 1 + x to P2(x)=1+x+12x2 P_2(x) = 1 + x + \frac{1}{2}x^2 , the polynomial matches higher derivatives and hugs the exponential curve with rapidly diminishing error near the center.
A particle moves in the xyxy-plane with position given by x(t)=t3−3tx(t) = t^3 - 3t and y(t)=2t2+1y(t) = 2t^2 + 1 for t>0t > 0. Find the slope of the tangent line dydx\frac{dy}{dx} at t=2t = 2.
Compute individual derivatives: dxdt=3t2−3\frac{dx}{dt} = 3t^2 - 3 and dydt=4t\frac{dy}{dt} = 4t. At t=2t = 2, dxdt=3(4)−3=9\frac{dx}{dt} = 3(4) - 3 = 9 and dydt=4(2)=8\frac{dy}{dt} = 4(2) = 8. The parametric slope is dydx=dy/dtdx/dt=89\frac{dy}{dx} = \frac{dy/dt}{dx/dt} = \frac{8}{9}.
📝 Chapter Quiz
1

Advanced Integration Techniques

📌 AP Calc BC BC-1 — Advanced Integration 17–20% of exam  ·  Integration by parts  ·  Partial fractions  ·  Improper integrals

BC extends the integral toolkit with integration by parts, partial fractions, and improper integrals over infinite or unbounded intervals.

▲ Reference — Three new tools

By parts: ∫u dv=uv−∫v du \displaystyle\int u\,dv=uv-\int v\,du . Partial fractions split a rational integrand into simpler pieces. Improper integrals are limits: ∫a∞f=lim⁡b→∞∫abf \displaystyle\int_a^{\infty} f=\lim_{b\to\infty}\int_a^{b} f .

Improper Integral: Area Under f(x) = 1/x² from x = 1 to ∞ — Coordinate plane with graph of f(x) = 1/x²; marked points (1, 1) (1, 1), (2, 0.25) (2, 0.25)123451xyf(x) = 1/x²(1, 1)(2, 0.25)y = 0
The improper integral ∫1∞1x2 dx=lim⁡b→∞[1−1b]=1 \int_1^\infty \frac{1}{x^2}\,dx = \lim_{b\to\infty} \left[1 - \frac{1}{b}\right] = 1 . Even though the domain extends infinitely along the horizontal axis, the accumulated area converges to exactly 1 1 .
By parts
uv−∫v du uv-\displaystyle\int v\,du
Partial fractions
1(x−a)(x−b) \dfrac{1}{(x-a)(x-b)}
Improper
lim⁡b→∞∫abf \displaystyle\lim_{b\to\infty}\int_a^b f
Arctangent
∫dxx2+a2=1aarctan⁡xa \displaystyle\int\dfrac{dx}{x^{2}+a^{2}}=\dfrac1a\arctan\dfrac{x}{a}
⚠️ AP Exam Traps: Advanced Integration Techniques
  • Mandatory Limit Notation on FRQs: You cannot plug ∞ \infty directly into an antiderivative bracket on the AP Exam. Writing [−1x]1∞ \left[-\frac{1}{x}\right]_1^\infty loses the setup point. You MUST replace ∞ \infty with a dummy variable and take the limit: lim⁡b→∞∫1b1x2 dx=lim⁡b→∞[−1x]1b \lim_{b\to\infty} \int_1^b \frac{1}{x^2}\,dx = \lim_{b\to\infty}\left[-\frac{1}{x}\right]_1^b .
  • Integration by Parts Sign Distribution: In ∫u dv=uv−∫v du \int u\,dv = uv - \int v\,du , when performing repeated IBP or when v v contains a negative sign (e.g. ∫sin⁡(x)dx=−cos⁡(x) \int \sin(x)dx = -\cos(x) ), parenthesize carefully: −(−uv) -(-uv) turns into a + + , and a negative outside distributed over an inner subtraction is the single most frequent calculation error.
  • Improper Integrals with Interior Discontinuities: Watch out for integrals like ∫−111x2 dx \int_{-1}^1 \frac{1}{x^2}\,dx . The integrand is undefined at x=0 x=0 , so you cannot apply the Fundamental Theorem of Calculus directly. It must be split into ∫−101x2 dx+∫011x2 dx \int_{-1}^0 \frac{1}{x^2}\,dx + \int_0^1 \frac{1}{x^2}\,dx , both of which diverge to ∞ \infty .
  • LIATE Priority Rule for Parts: Pick u u following Logarithmic, Inverse trig, Algebraic (polynomials), Trigonometric, Exponential. Differentiate u u and integrate dv dv .
Worked example · By parts

Evaluate ∫xex dx \displaystyle\int x e^{x}\,dx with u=x, dv=exdx u=x,\ dv=e^{x}dx . xex−∫ex dx=(x−1)ex+C. x e^{x}-\int e^{x}\,dx=(x-1)e^{x}+C.

Worked example — Integration by parts

Evaluate ∫x2ex dx\displaystyle\int x^2 e^x\,dx.

Apply IBP twice. Let u=x2, dv=exdxu=x^2,\,dv=e^x dx: x2ex−2∫xexdxx^2e^x-2\int xe^x dx.

For ∫xexdx\int xe^x dx: u=x, dv=exdx⇒xex−exu=x,\,dv=e^x dx\Rightarrow xe^x-e^x.

∫x2ex dx=x2ex−2xex+2ex+c=ex(x2−2x+2)+c.\int x^2e^x\,dx=x^2e^x-2xe^x+2e^x+c=e^x(x^2-2x+2)+c.

Determine whether ∫1∞1x2 dx\displaystyle\int_1^\infty\frac{1}{x^2}\,dx converges, and if so find its value.
∫1b1x2dx=[−1x]1b=1−1b→1\int_1^b\frac{1}{x^2}dx=\left[-\frac{1}{x}\right]_1^b=1-\frac{1}{b}\to1 as b→∞b\to\infty. Converges to 11.
Evaluate the definite integral ∫0πxsin⁡x dx\displaystyle\int_0^\pi x \sin x\,dx using integration by parts.
Let u=xu = x and dv=sin⁡x dxdv = \sin x\,dx. Then du=dxdu = dx and v=−cos⁡xv = -\cos x. Applying IBP: ∫xsin⁡x dx=−xcos⁡x−∫(−cos⁡x) dx=−xcos⁡x+sin⁡x\int x\sin x\,dx = -x\cos x - \int(-\cos x)\,dx = -x\cos x + \sin x. Evaluating from 00 to π\pi: [−πcos⁡(π)+sin⁡(π)]−[−0cos⁡(0)+sin⁡(0)]=[−π(−1)+0]−0=π[-\pi\cos(\pi) + \sin(\pi)] - [-0\cos(0) + \sin(0)] = [-\pi(-1) + 0] - 0 = \pi.
📝 Chapter Quiz
2

Logistic Models & Euler's Method

📌 AP Calc BC BC-2 — Logistic & Euler's Method 6–12% of exam  ·  Logistic growth model  ·  Euler's method  ·  Long-run behaviour

BC adds a richer population model and a numerical method for approximating solutions to differential equations.

▲ Reference — Growth & approximation

Logistic: dPdt=kP ⁣(1−PM) \dfrac{dP}{dt}=kP\!\left(1-\dfrac{P}{M}\right) , carrying capacity M M , fastest growth at P=M2 P=\tfrac{M}{2} . Euler's method steps forward: yn+1=yn+h f(xn,yn) y_{n+1}=y_n+h\,f(x_n,y_n) .

Logistic Growth Curve: Carrying Capacity and Inflection Point — Coordinate plane with graph of P(t) = 10 / (1 + 9e^{-0.9t}); marked points P(0) = 1 (0, 1), Inflection at P = M/2 = 5 (2.44, 5)1234567246810xyP(t) = 10 / (1 + 9e^{-0.9t})P(0) = 1Inflection at P = M/2 = 5Carrying capacity M = 10P = M/2 = 5
Logistic growth curve P(t)=101+9e−0.9t P(t) = \frac{10}{1 + 9e^{-0.9t}} with carrying capacity M=10 M=10 . Growth is fastest at the inflection point where P=M/2=5 P = M/2 = 5 and d2Pdt2=0 \frac{d^2P}{dt^2} = 0 . The curve is concave up on (0,2.44) (0, 2.44) and concave down on (2.44,∞) (2.44, \infty) .
Logistic ODE
kP ⁣(1−PM) kP\!\left(1-\tfrac{P}{M}\right)
Carrying capacity
lim⁡t→∞P=M \lim_{t\to\infty}P=M
Fastest growth
P=M2 P=\tfrac{M}{2}
Euler step
yn+hf(xn,yn) y_n+h f(x_n,y_n)
⚠️ AP Exam Traps: Logistic Models & Euler's Method
  • Fastest Growth is at Population P=M/2 P = M/2 , NOT Time t=M/2 t = M/2 : When the exam asks 'for what population is the growth rate greatest?', the answer is always half the carrying capacity M/2 M/2 . If it asks 'at what time is the growth rate greatest?', substitute P=M/2 P = M/2 into the particular solution and solve for t t .
  • Factoring Non-Standard Logistic Forms: If given dPdt=0.2P−0.0005P2 \frac{dP}{dt} = 0.2P - 0.0005P^2 , factor out 0.2P 0.2P : 0.2P(1−0.00050.2P)=0.2P(1−P400) 0.2P\left(1 - \frac{0.0005}{0.2}P\right) = 0.2P\left(1 - \frac{P}{400}\right) . The carrying capacity is M=400 M = 400 , not 0.0005 0.0005 or 0.2 0.2 !
  • Euler Concavity Error Analysis: Free-response questions frequently ask whether Euler's method overestimates or underestimates the true solution y(b) y(b) :
    • If y′′(x)>0 y''(x) > 0 (concave up), tangent lines lie below the curve ⇒ \Rightarrow Euler's method underestimates.
    • If y′′(x)<0 y''(x) < 0 (concave down), tangent lines lie above the curve ⇒ \Rightarrow Euler's method overestimates.
  • Never Combine Steps in Euler's Method: Always calculate the slope f(xn,yn) f(x_n, y_n) and step explicitly: yn+1=yn+Δx⋅f(xn,yn) y_{n+1} = y_n + \Delta x \cdot f(x_n, y_n) . AP readers require evidence of step-by-step arithmetic.
Worked example · Euler step

For dydx=y, y(0)=1 \dfrac{dy}{dx}=y,\ y(0)=1 , take one Euler step with h=0.5 h=0.5 . y(0.5)≈1+0.5⋅1=1.5. y(0.5)\approx 1+0.5\cdot 1=1.5.

Worked example — Euler's method

Use Euler's method with step h=0.1h=0.1 to approximate y(0.2)y(0.2) for dydx=y−x\dfrac{dy}{dx}=y-x, y(0)=1y(0)=1.

y1=y0+hf(x0,y0)=1+0.1(1−0)=1.1y_1=y_0+hf(x_0,y_0)=1+0.1(1-0)=1.1.

y2=y1+hf(x1,y1)=1.1+0.1(1.1−0.1)=1.1+0.1=1.2y_2=y_1+hf(x_1,y_1)=1.1+0.1(1.1-0.1)=1.1+0.1=1.2.

The logistic model dPdt=0.4P ⁣(1−P500)\dfrac{dP}{dt}=0.4P\!\left(1-\dfrac{P}{500}\right) has P(0)=50P(0)=50. What is lim⁡t→∞P(t)\lim_{t\to\infty}P(t)? For what PP is the growth rate greatest?
Carrying capacity K=500K=500. lim⁡P=500\lim P=500. Maximum growth rate at P=K/2=250P=K/2=250.
Let dydx=2x−y\dfrac{dy}{dx} = 2x - y with initial condition y(0)=2y(0) = 2. Use Euler's method with two steps of equal size h=0.5h = 0.5 to approximate y(1)y(1).
Step 1: At (x0,y0)=(0,2)(x_0, y_0) = (0, 2), slope f(0,2)=2(0)−2=−2f(0, 2) = 2(0) - 2 = -2. Then y1=y0+h⋅f(0,2)=2+0.5(−2)=1y_1 = y_0 + h\cdot f(0, 2) = 2 + 0.5(-2) = 1 at x1=0.5x_1 = 0.5.
Step 2: At (x1,y1)=(0.5,1)(x_1, y_1) = (0.5, 1), slope f(0.5,1)=2(0.5)−1=1−1=0f(0.5, 1) = 2(0.5) - 1 = 1 - 1 = 0. Then y2=y1+h⋅f(0.5,1)=1+0.5(0)=1y_2 = y_1 + h\cdot f(0.5, 1) = 1 + 0.5(0) = 1 at x2=1.0x_2 = 1.0.
Therefore, y(1)≈1y(1) \approx 1.
📝 Chapter Quiz
3

Parametric & Vector-Valued Functions

📌 AP Calc BC BC-3 — Parametric & Vectors 11–12% of exam  ·  Parametric derivatives & arc length  ·  Vector-valued functions & motion

When a curve is traced by a parameter t t , motion in the plane is captured by component functions and their derivatives.

▲ Reference — Parametric calculus

dydx=dy/dtdx/dt \dfrac{dy}{dx}=\dfrac{dy/dt}{dx/dt} . Speed is (dx/dt)2+(dy/dt)2 \sqrt{(dx/dt)^{2}+(dy/dt)^{2}} , and arc length is ∫(dx/dt)2+(dy/dt)2 dt \displaystyle\int\sqrt{(dx/dt)^{2}+(dy/dt)^{2}}\,dt . A vector position r(t)=⟨x(t),y(t)⟩ \mathbf r(t)=\langle x(t),y(t)\rangle has velocity r′(t) \mathbf r'(t) .

Parametric Trajectory and Tangent Vector: x = t², y = t³ — Coordinate plane with graph of Trajectory y = x^{3/2}, Tangent at t = 1 (slope = 1.5); marked points t = 0 (origin) (0, 0), t = 1: (1, 1) (1, 1)12312345xyTrajectory y = x^{3/2}Tangent at t = 1 (slope = 1.5)t = 0 (origin)t = 1: (1, 1)y = 0
Parametric trajectory x(t)=t2,y(t)=t3 x(t) = t^2, y(t) = t^3 (Cartesian form y=x3/2 y = x^{3/2} ). At t=1 t=1 , the particle is at (1,1) (1,1) with velocity vector v⃗(1)=⟨2,3⟩ \vec{v}(1) = \langle 2, 3 \rangle , yielding tangent line slope dydx=32=1.5 \frac{dy}{dx} = \frac{3}{2} = 1.5 .
Slope
dy/dtdx/dt \dfrac{dy/dt}{dx/dt}
Speed
x′2+y′2 \sqrt{x'^{2}+y'^{2}}
Arc length
∫x′2+y′2 dt \displaystyle\int\sqrt{x'^{2}+y'^{2}}\,dt
Velocity
⟨x′(t),y′(t)⟩ \langle x'(t),y'(t)\rangle
⚠️ AP Exam Traps: Parametric & Vector Calculus
  • The Second Derivative Formula: The second derivative with respect to x x is d2ydx2=ddt[dydx]dxdt \frac{d^2y}{dx^2} = \frac{\frac{d}{dt}\left[\frac{dy}{dx}\right]}{\frac{dx}{dt}} . It is NEVER y′′(t)x′′(t) \frac{y''(t)}{x''(t)} ! You must differentiate dydx \frac{dy}{dx} with respect to t t and then divide the entire result by dxdt \frac{dx}{dt} .
  • Speed vs. Velocity Vector: Velocity is a vector with direction: v⃗(t)=⟨x′(t),y′(t)⟩ \vec{v}(t) = \langle x'(t), y'(t) \rangle . Speed is a scalar magnitude: Speed=∥v⃗(t)∥=(x′(t))2+(y′(t))2 \text{Speed} = \|\vec{v}(t)\| = \sqrt{(x'(t))^2 + (y'(t))^2} . Always check whether a question asks for speed or velocity.
  • Total Distance vs. Displacement:
    • Total distance traveled is the integral of speed: ∫ab(x′(t))2+(y′(t))2 dt \int_a^b \sqrt{(x'(t))^2 + (y'(t))^2}\,dt .
    • Displacement is the vector net change: ⟨x(b)−x(a),y(b)−y(a)⟩ \langle x(b) - x(a), y(b) - y(a) \rangle .
  • Particle at Rest: A particle is at rest if and only if both components are simultaneously zero: x′(t)=0 x'(t) = 0 and y′(t)=0 y'(t) = 0 . If only x′(t)=0 x'(t) = 0 , the curve has a vertical tangent; if only y′(t)=0 y'(t) = 0 , the curve has a horizontal tangent.
Worked example · Parametric slope

For x=t2, y=t3 x=t^{2},\ y=t^{3} , find dydx \dfrac{dy}{dx} . dydx=3t22t=3t2. \frac{dy}{dx}=\frac{3t^{2}}{2t}=\frac{3t}{2}.

Worked example — Parametric arc length

Find the arc length of x=t2,  y=23t3x=t^2,\;y=\tfrac{2}{3}t^3 from t=0t=0 to t=1t=1.dxdt=2t,dydt=2t2.\frac{dx}{dt}=2t,\quad\frac{dy}{dt}=2t^2.L=∫014t2+4t4 dt=∫012t1+t2 dt=[23(1+t2)3/2]01=23(23/2−1)=2(22−1)3.L=\int_0^1\sqrt{4t^2+4t^4}\,dt=\int_0^1 2t\sqrt{1+t^2}\,dt=\left[\tfrac{2}{3}(1+t^2)^{3/2}\right]_0^1=\tfrac{2}{3}(2^{3/2}-1)=\tfrac{2(2\sqrt2-1)}{3}.

A particle moves with x(t)=cos⁡t,  y(t)=sin⁡tx(t)=\cos t,\;y(t)=\sin t. Find the speed at t=π/4t=\pi/4 and the total distance travelled from t=0t=0 to t=πt=\pi.
Speed =x˙2+y˙2=sin⁡2t+cos⁡2t=1=\sqrt{\dot x^2+\dot y^2}=\sqrt{\sin^2t+\cos^2t}=1 (constant). Distance =∫0π1 dt=π=\int_0^\pi1\,dt=\pi.
A curve is given parametrically by x(t)=t3−3tx(t) = t^3 - 3t and y(t)=t2y(t) = t^2. Find d2ydx2\dfrac{d^2y}{dx^2} at t=2t = 2.
First compute derivatives: x′(t)=3t2−3x'(t) = 3t^2 - 3 and y′(t)=2ty'(t) = 2t. The first derivative is dydx=2t3t2−3\frac{dy}{dx} = \frac{2t}{3t^2 - 3}. Next differentiate with respect to tt using the quotient rule: ddt[dydx]=(3t2−3)(2)−(2t)(6t)(3t2−3)2=6t2−6−12t2(3t2−3)2=−6t2−6(3t2−3)2\frac{d}{dt}\left[\frac{dy}{dx}\right] = \frac{(3t^2 - 3)(2) - (2t)(6t)}{(3t^2 - 3)^2} = \frac{6t^2 - 6 - 12t^2}{(3t^2 - 3)^2} = \frac{-6t^2 - 6}{(3t^2 - 3)^2}. At t=2t = 2, 3(2)2−3=93(2)^2 - 3 = 9, so ddt[dydx]=−6(4)−692=−3081=−1027\frac{d}{dt}\left[\frac{dy}{dx}\right] = \frac{-6(4)-6}{9^2} = \frac{-30}{81} = -\frac{10}{27}. Finally, d2ydx2=−10/27x′(2)=−10/279=−10243\frac{d^2y}{dx^2} = \frac{-10/27}{x'(2)} = \frac{-10/27}{9} = -\frac{10}{243}.
📝 Chapter Quiz
4

Polar Coordinates

📌 AP Calc BC BC-4 — Polar Coordinates 5–6% of exam  ·  Converting polar/rectangular  ·  Polar area formula  ·  Polar curve derivatives

Polar coordinates locate points by radius and angle, and turn area into a sweep of the radius about the origin.

The polar curve r=sin⁡(kθ) r=\sin(k\theta) traces a rose. Change k k and count the petals — odd k k gives k k petals, even k k gives 2k 2k .

⊙ Explorer · Polar roseinteractive
petals—

Polar area is 12∫r2 dθ \tfrac12\displaystyle\int r^{2}\,d\theta — one of the headline BC integrals.

▲ Reference — Polar calculus

Convert with x=rcos⁡θ, y=rsin⁡θ x=r\cos\theta,\ y=r\sin\theta . The area swept is A=12∫αβr2 dθ A=\tfrac12\displaystyle\int_\alpha^\beta r^{2}\,d\theta . Slope follows from treating x x and y y as parametric in θ \theta .

Circle centered at O with radius r with shaded sector θθOr
Polar area is generated as the radial arm r(θ) r(\theta) sweeps through angle dθ d\theta , creating an infinitesimal circular sector with area dA=12r2 dθ dA = \frac{1}{2} r^2\,d\theta . Integrating across [α,β] [\alpha, \beta] yields the total enclosed area A=12∫αβr2 dθ A = \frac{1}{2}\int_\alpha^\beta r^2\,d\theta .
Conversion
x=rcos⁡θ, y=rsin⁡θ x=r\cos\theta,\ y=r\sin\theta
Polar area
12∫r2 dθ \tfrac12\displaystyle\int r^{2}\,d\theta
Circle
r=a r=a
Cardioid
r=a(1±cos⁡θ) r=a(1\pm\cos\theta)
⚠️ AP Exam Traps: Polar Coordinates & Calculus
  • The Missing 12 \frac{1}{2} Factor: The single most frequent student error in polar integration is omitting the 12 \frac{1}{2} factor. Always write A=12∫αβr2 dθ A = \frac{1}{2} \int_\alpha^\beta r^2\,d\theta .
  • Area Between Two Polar Curves: If region R R lies between outer curve r1(θ) r_1(\theta) and inner curve r2(θ) r_2(\theta) , the area is 12∫[r12−r22] dθ \frac{1}{2} \int [r_1^2 - r_2^2]\,d\theta . It is NEVER 12∫[r1−r2]2 dθ \frac{1}{2}\int [r_1 - r_2]^2\,d\theta !
  • Polar Slope dydx \frac{dy}{dx} vs. drdθ \frac{dr}{d\theta} : The derivative drdθ \frac{dr}{d\theta} measures how fast the radius grows with respect to angle — it is NOT the slope of the tangent line. To find slope, apply the product rule to y=rsin⁡θ y = r\sin\theta and x=rcos⁡θ x = r\cos\theta : dydx=dydθdxdθ=r′sin⁡θ+rcos⁡θr′cos⁡θ−rsin⁡θ. \frac{dy}{dx} = \frac{\frac{dy}{d\theta}}{\frac{dx}{d\theta}} = \frac{r'\sin\theta + r\cos\theta}{r'\cos\theta - r\sin\theta}.
  • Petal Bounds: To find integration limits for a single petal, find consecutive angles where r(θ)=0 r(\theta) = 0 . For r=sin⁡(2θ) r = \sin(2\theta) , 2θ=0⇒θ=0 2\theta = 0 \Rightarrow \theta = 0 and 2θ=π⇒θ=π/2 2\theta = \pi \Rightarrow \theta = \pi/2 , so the petal spans [0,π/2] [0, \pi/2] .
Worked example · Polar area

Find the area enclosed by r=2 r=2 . 12∫02π22 dθ=12⋅4⋅2π=4π. \tfrac12\int_0^{2\pi}2^{2}\,d\theta=\tfrac12\cdot4\cdot2\pi=4\pi.

Worked example — Polar area

Find the area enclosed by one petal of r=sin⁡(2θ)r=\sin(2\theta).

One petal: 0≤θ≤π/20\leq\theta\leq\pi/2.

A=12∫0π/2sin⁡2(2θ) dθ=12∫0π/21−cos⁡(4θ)2 dθ=π8.A=\tfrac{1}{2}\int_0^{\pi/2}\sin^2(2\theta)\,d\theta=\tfrac{1}{2}\int_0^{\pi/2}\frac{1-\cos(4\theta)}{2}\,d\theta=\frac{\pi}{8}.

Convert the polar equation r=4cos⁡θr=4\cos\theta to rectangular form and identify the curve.
Multiply both sides by rr: r2=4rcos⁡θ⇒x2+y2=4x⇒(x−2)2+y2=4r^2=4r\cos\theta\Rightarrow x^2+y^2=4x\Rightarrow(x-2)^2+y^2=4. Circle, centre (2,0)(2,0), radius 22.
Find the slope of the line tangent to the cardioid r=1+cos⁡θr = 1 + \cos\theta at θ=π2\theta = \frac{\pi}{2}.
Write rectangular coordinates in terms of θ\theta: x=(1+cos⁡θ)cos⁡θ=cos⁡θ+cos⁡2θx = (1+\cos\theta)\cos\theta = \cos\theta + \cos^2\theta, and y=(1+cos⁡θ)sin⁡θ=sin⁡θ+sin⁡θcos⁡θy = (1+\cos\theta)\sin\theta = \sin\theta + \sin\theta\cos\theta. Differentiate: dxdθ=−sin⁡θ−2cos⁡θsin⁡θ\frac{dx}{d\theta} = -\sin\theta - 2\cos\theta\sin\theta; at θ=π/2\theta = \pi/2, dxdθ=−1−0=−1\frac{dx}{d\theta} = -1 - 0 = -1. Next, dydθ=cos⁡θ+cos⁡2θ−sin⁡2θ\frac{dy}{d\theta} = \cos\theta + \cos^2\theta - \sin^2\theta; at θ=π/2\theta = \pi/2, dydθ=0+0−1=−1\frac{dy}{d\theta} = 0 + 0 - 1 = -1. Thus, the tangent slope is dydx=−1−1=1\frac{dy}{dx} = \frac{-1}{-1} = 1.
📝 Chapter Quiz
5

Infinite Sequences & Series — Convergence

📌 AP Calc BC BC-5 — Sequences & Series 17–18% of exam  ·  Convergence tests  ·  Alternating series error bound  ·  Absolute vs. conditional

The heart of BC: deciding whether an infinite sum settles to a finite value, using a battery of convergence tests.

Watch the geometric series ∑n≥1(12)n \sum_{n\ge1}\left(\tfrac12\right)^{n} converge: each partial sum SN S_N climbs toward the limit 1 1 (the amber line).

⊙ Explorer · Partial sumsinteractive
partial sum S_N—

SN=1−(12)N→1 S_N=1-\left(\tfrac12\right)^{N}\to1 ; a geometric series converges because ∣r∣<1 |r|<1 .

▲ Reference — Convergence tests

nth-term test: if an↛0 a_n\not\to0 , the series diverges. A geometric series converges when ∣r∣<1 |r|<1 ; a p-series when p>1 p>1 . The comparison, ratio, and alternating series tests handle the rest.

Convergence of Geometric Partial Sums: S_N = 1 - (1/2)^N — Coordinate plane with graph of S(n) = 1 - (1/2)ⁿ; marked points S₁ = 0.5 (1, 0.5), S₂ = 0.75 (2, 0.75), S₃ = 0.875 (3, 0.875), S₄ = 0.938 (4, 0.938)123451xyS(n) = 1 − (1/2)ⁿS₁ = 0.5S₂ = 0.75S₃ = 0.875S₄ = 0.938Sum S = 1
Partial sums SN=∑n=1N(1/2)n=1−(1/2)N S_N = \sum_{n=1}^N (1/2)^n = 1 - (1/2)^N climb monotonically toward the horizontal asymptote S=1 S = 1 . Because ∣r∣=1/2<1 |r| = 1/2 < 1 , the infinite series converges to a1−r=1/21−1/2=1 \frac{a}{1-r} = \frac{1/2}{1 - 1/2} = 1 .
Geometric
∑arn=a1−r \displaystyle\sum ar^{n}=\dfrac{a}{1-r}
p-series
converges if p>1 p>1
Ratio test
lim⁡∣an+1an∣<1 \lim\left|\dfrac{a_{n+1}}{a_n}\right|<1
Alternating
terms ↓0 \downarrow 0
⚠️ AP Exam Traps: Infinite Series Convergence Tests
  • The n n -th Term Divergence Test Never Proves Convergence: If lim⁡an≠0 \lim a_n \neq 0 , the series diverges. However, if lim⁡an=0 \lim a_n = 0 , the test is INCONCLUSIVE! The harmonic series ∑1n \sum \frac{1}{n} has terms approaching 0 0 , but it diverges. Never write 'converges by the n n -th term test' on an AP exam.
  • Ratio Test Inconclusiveness: If lim⁡∣an+1/an∣=1 \lim |a_{n+1}/a_n| = 1 , the Ratio Test fails completely. The Ratio Test cannot determine the convergence of p p -series or algebraic fractions (it always gives 1 1 ). Use the Limit Comparison Test with a p p -series instead.
  • Alternating Series Test (AST) Hypotheses: To earn full credit for AST on an FRQ, you must explicitly state that (1) terms alternate in sign, (2) terms decrease in magnitude (∣an+1∣≤∣an∣ |a_{n+1}| \le |a_n| ), and (3) lim⁡n→∞∣an∣=0 \lim_{n\to\infty} |a_n| = 0 .
  • Alternating Error Bound: If an alternating series converges by AST, the truncation error when using the N N -th partial sum SN S_N is bounded by the magnitude of the first omitted term: ∣S−SN∣≤∣aN+1∣ |S - S_N| \le |a_{N+1}| .
Worked example · Geometric sum

Evaluate ∑n=1∞(12)n \displaystyle\sum_{n=1}^{\infty}\left(\tfrac12\right)^{n} . 121−12=1. \frac{\tfrac12}{1-\tfrac12}=1.

Worked example — Ratio test

Determine whether ∑n=1∞n!nn\displaystyle\sum_{n=1}^\infty\dfrac{n!}{n^n} converges.L=lim⁡n→∞(n+1)!/(n+1)n+1n!/nn=lim⁡n→∞nn(n+1)n=lim⁡n→∞(nn+1)n=1e<1.L=\lim_{n\to\infty}\frac{(n+1)!/(n+1)^{n+1}}{n!/n^n}=\lim_{n\to\infty}\frac{n^n}{(n+1)^n}=\lim_{n\to\infty}\left(\frac{n}{n+1}\right)^n=\frac{1}{e}<1.

Ratio test: L<1L<1, so the series converges.

Find the interval of convergence of ∑n=1∞(−1)nxnn\displaystyle\sum_{n=1}^\infty\dfrac{(-1)^n x^n}{n}.
Ratio test: ∣x∣|x|. Converges absolutely for ∣x∣<1|x|<1. At x=1x=1: alternating harmonic series, converges. At x=−1x=-1: harmonic series, diverges. Interval of convergence: −1<x≤1-1<x\leq1.
Determine whether the series ∑n=1∞(−1)nn\displaystyle\sum_{n=1}^\infty\frac{(-1)^n}{\sqrt{n}} converges absolutely, converges conditionally, or diverges.
First test absolute convergence: ∑∣(−1)nn∣=∑1n1/2\sum\left|\frac{(-1)^n}{\sqrt{n}}\right| = \sum\frac{1}{n^{1/2}}. This is a pp-series with p=1/2≤1p = 1/2 \le 1, which diverges. Next test the original alternating series using AST: the terms alternate in sign, bn=1nb_n = \frac{1}{\sqrt{n}} is strictly decreasing (bn+1<bnb_{n+1} < b_n), and lim⁡n→∞1n=0\lim_{n\to\infty}\frac{1}{\sqrt{n}} = 0. By the Alternating Series Test, the series converges. Since the series converges but does not converge absolutely, it converges conditionally.
📝 Chapter Quiz
6

Power, Taylor & Maclaurin Series

📌 AP Calc BC BC-6 — Power, Taylor & Maclaurin 17–18% of exam  ·  Taylor/Maclaurin series  ·  Radius & interval of convergence  ·  Lagrange error

Functions can be rebuilt as infinite polynomials, exact within an interval of convergence — the capstone of the course.

The amber Maclaurin polynomial for sin⁡x \sin x hugs the true curve (indigo) ever more widely as you add terms.

⊙ Explorer · Taylor polynomialinteractive
polynomial degree—

sin⁡x=x−x33!+x55!−⋯ \sin x = x-\dfrac{x^{3}}{3!}+\dfrac{x^{5}}{5!}-\cdots — convergent for all x x .

▲ Reference — Series for functions

The Taylor series about a a is ∑f(n)(a)n!(x−a)n \displaystyle\sum \frac{f^{(n)}(a)}{n!}(x-a)^{n} ; centred at 0 0 it is a Maclaurin series. Memorise the series for ex e^{x} , sin⁡x \sin x , cos⁡x \cos x and 11−x \tfrac{1}{1-x} , each with its interval of convergence.

Maclaurin Polynomial Approximations: f(x) = sin(x) vs P₁(x) and P₃(x) — Coordinate plane with graph of f(x) = sin(x), P₁(x) = x, P₃(x) = x - x³/6; marked points Center (0,0) (0, 0)-3-2-1123-2-112xyf(x) = sin(x)P₁(x) = xP₃(x) = x − x³/6Center (0,0)y = 0
Maclaurin polynomial approximations for f(x)=sin⁡(x) f(x) = \sin(x) centered at x=0 x=0 . The tangent line P1(x)=x P_1(x) = x is accurate only near the origin, whereas the cubic polynomial P3(x)=x−x33! P_3(x) = x - \frac{x^3}{3!} hugs the curve closely across [−π/2,π/2] [-\pi/2, \pi/2] .
Taylor
∑f(n)(a)n!(x−a)n \displaystyle\sum\dfrac{f^{(n)}(a)}{n!}(x-a)^{n}
Exponential
ex=∑xnn! e^{x}=\displaystyle\sum\dfrac{x^{n}}{n!}
Geometric
11−x=∑xn \dfrac{1}{1-x}=\displaystyle\sum x^{n}
Convergence
radius / interval
⚠️ AP Exam Traps: Taylor Series & Error Bounds
  • Don't Forget the Factorial Denominator: In the Taylor coefficient formula cn=f(n)(a)n! c_n = \frac{f^{(n)}(a)}{n!} , the denominator is n! n! , not n n . If given f′′′(2)=18 f'''(2) = 18 , the coefficient of (x−2)3 (x-2)^3 is 183!=186=3 \frac{18}{3!} = \frac{18}{6} = 3 , not 18 18 !
  • Alternating Series Error vs. Lagrange Error Bound:
    • If a series alternates with terms decreasing in magnitude to zero, the truncation error is bounded simply by the first omitted term: ∣Rn(x)∣≤∣an+1∣ |R_n(x)| \le |a_{n+1}| .
    • If the series is not alternating, or if the question explicitly asks for the Lagrange Error Bound, use: ∣Rn(x)∣≤M(n+1)!∣x−a∣n+1 |R_n(x)| \le \frac{M}{(n+1)!}|x-a|^{n+1} , where M=max⁡t∈[a,x]∣f(n+1)(t)∣ M = \max_{t \in [a, x]} |f^{(n+1)}(t)| .
  • Endpoints in the Interval of Convergence: Finding the radius of convergence R R via the Ratio Test does NOT determine the interval endpoints. You must independently test both endpoints x=a−R x = a - R and x=a+R x = a + R using other convergence tests (p-series, AST, or comparison).
  • Substitute into Known Series: When finding series like cos⁡(x2) \cos(x^2) or xe−x x e^{-x} , never take multiple derivatives. Instead, substitute directly into the standard series for cos⁡u \cos u or eu e^u and simplify.
Worked example · Maclaurin of ex e^{x}

Write the Maclaurin series for ex e^{x} . ex=1+x+x22!+x33!+⋯=∑n=0∞xnn!. e^{x}=1+x+\frac{x^{2}}{2!}+\frac{x^{3}}{3!}+\cdots=\sum_{n=0}^{\infty}\frac{x^{n}}{n!}.

Worked example — Lagrange error bound

The Maclaurin series for cos⁡x\cos x is 1−x22!+x44!−⋯1-\dfrac{x^2}{2!}+\dfrac{x^4}{4!}-\cdots. Use the Lagrange error bound to bound the error when approximating cos⁡(0.1)\cos(0.1) with the first two non-zero terms.

Using P2(x)=1−x22P_2(x)=1-\dfrac{x^2}{2}. Error ≤∣x∣44!⋅max⁡∣f(4)∣\leq\dfrac{|x|^4}{4!}\cdot\max|f^{(4)}|. Since ∣f(4)∣=∣cos⁡c∣≤1|f^{(4)}|=|\cos c|\leq1:

∣E∣≤(0.1)424=0.000124≈4.2×10−6.|E|\leq\frac{(0.1)^4}{24}=\frac{0.0001}{24}\approx4.2\times10^{-6}.

Find the first three terms of the Taylor series for f(x)=ln⁡(1+x)f(x)=\ln(1+x) centred at x=0x=0 and state its radius of convergence.
f(0)=0f(0)=0, f′(0)=1f'(0)=1, f′′(0)=−1f''(0)=-1. ln⁡(1+x)=x−x22+x33−⋯\ln(1+x)=x-\dfrac{x^2}{2}+\dfrac{x^3}{3}-\cdots Radius of convergence R=1R=1.
A function ff has derivatives of all orders with f(2)=3f(2) = 3, f′(2)=−4f'(2) = -4, f′′(2)=6f''(2) = 6, and f′′′(2)=−12f'''(2) = -12. Write the third-degree Taylor polynomial P3(x)P_3(x) for ff centered at x=2x = 2.
Using the Taylor polynomial formula P3(x)=f(2)+f′(2)(x−2)+f′′(2)2!(x−2)2+f′′′(2)3!(x−2)3P_3(x) = f(2) + f'(2)(x-2) + \frac{f''(2)}{2!}(x-2)^2 + \frac{f'''(2)}{3!}(x-2)^3:
Substitute the given derivatives:
P3(x)=3−4(x−2)+62!(x−2)2+−123!(x−2)3=3−4(x−2)+3(x−2)2−2(x−2)3.P_3(x) = 3 - 4(x-2) + \frac{6}{2!}(x-2)^2 + \frac{-12}{3!}(x-2)^3 = 3 - 4(x-2) + 3(x-2)^2 - 2(x-2)^3.
📝 Chapter Quiz
✶

Worked FRQs

Taylor series template
f(x)=∑n=0∞f(n)(a)n!(x−a)n f(x)=\sum_{n=0}^\infty\dfrac{f^{(n)}(a)}{n!}(x-a)^n
Lagrange error bound
∣Rn∣≤M∣x−a∣n+1(n+1)! |R_n|\leq\dfrac{M|x-a|^{n+1}}{(n+1)!}
Polar area
A=12∫αβr2 dθ A=\dfrac{1}{2}\int_\alpha^\beta r^2\,d\theta
Series convergence
Apply ratio test; check endpoints; state interval of convergence
Parametric FRQ Trajectory: x(t) = t², y(t) = t³ - 3t — Coordinate plane with graph of Path (t ≥ 0): y = x^{3/2} - 3√x, Tangent at t = 2 (slope = 9/4); marked points t = 0 (origin) (0, 0), t = √3: (3, 0) (3, 0), t = 2: (4, 2), slope = 9/4 (4, 2)12345-2246xyPath (t ≥ 0): y = x^{3/2} − 3√xTangent at t = 2 (slope = 9/4)t = 0 (origin)t = √3: (3, 0)t = 2: (4, 2), slope = 9/4y = 0
Parametric trajectory for FRQ 1: x(t)=t2,y(t)=t3−3t x(t) = t^2, y(t) = t^3 - 3t . At parameter value t=2 t=2 , the position is (4,2) (4, 2) and the slope of the tangent line is dydx=3t2−32t∣t=2=94=2.25 \frac{dy}{dx} = \frac{3t^2 - 3}{2t}\Big|_{t=2} = \frac{9}{4} = 2.25 .
FRQ 1 · Parametric motion

A curve is given by x(t)=t2 x(t)=t^2 , y(t)=t3−3t y(t)=t^3-3t . Find the slope dydx \dfrac{dy}{dx} at t=2 t=2 .

Differentiate each: dxdt=2t \dfrac{dx}{dt}=2t , dydt=3t2−3 \dfrac{dy}{dt}=3t^2-3 . Then

dydx=3t2−32t∣t=2=12−34=94. \frac{dy}{dx}=\frac{3t^2-3}{2t}\Big|_{t=2}=\frac{12-3}{4}=\frac{9}{4}.

FRQ 2 · Interval of convergence

Find the interval of convergence of ∑n=1∞xnn \displaystyle\sum_{n=1}^{\infty}\frac{x^n}{n} .

Ratio test: ∣xn+1/(n+1)xn/n∣=∣x∣⋅nn+1→∣x∣ \left|\dfrac{x^{n+1}/(n+1)}{x^n/n}\right|=|x|\cdot\dfrac{n}{n+1}\to|x| , so it converges for ∣x∣<1 |x|<1 . Check endpoints: x=1 x=1 gives the divergent harmonic series; x=−1 x=-1 gives the convergent alternating harmonic series.

Interval of convergence: [−1, 1). \text{Interval of convergence: } [-1,\,1).

FRQ 3 · Taylor Polynomial & Lagrange Error Bound

A function f f has derivatives of all orders with f(0)=2 f(0) = 2 , f′(0)=−3 f'(0) = -3 , f′′(0)=5 f''(0) = 5 , and f′′′(0)=−12 f'''(0) = -12 . The fourth derivative satisfies ∣f(4)(x)∣≤48 |f^{(4)}(x)| \le 48 for all x∈[0,0.5] x \in [0, 0.5] .

(a) Third-degree Taylor polynomial:P3(x)=f(0)+f′(0)x+f′′(0)2!x2+f′′′(0)3!x3=2−3x+52x2−2x3. P_3(x) = f(0) + f'(0)x + \frac{f''(0)}{2!}x^2 + \frac{f'''(0)}{3!}x^3 = 2 - 3x + \frac{5}{2}x^2 - 2x^3.

(b) Approximation at x=0.2 x = 0.2 :P3(0.2)=2−3(0.2)+2.5(0.04)−2(0.008)=2−0.6+0.1−0.016=1.484. P_3(0.2) = 2 - 3(0.2) + 2.5(0.04) - 2(0.008) = 2 - 0.6 + 0.1 - 0.016 = 1.484.

(c) Lagrange Error Bound: By the Lagrange Error Bound formula:∣f(0.2)−P3(0.2)∣≤max⁡∣f(4)(t)∣4!∣0.2−0∣4≤4824(0.0016)=2(0.0016)=0.0032. |f(0.2) - P_3(0.2)| \le \frac{\max |f^{(4)}(t)|}{4!}|0.2 - 0|^4 \le \frac{48}{24}(0.0016) = 2(0.0016) = 0.0032.

FRQ 4 · Polar Area & Rate of Change

A polar curve is defined by r=3+2cos⁡θ r = 3 + 2\cos\theta for 0≤θ≤2π 0 \le \theta \le 2\pi .

(a) Area enclosed by the curve:A=12∫02π(3+2cos⁡θ)2 dθ=12∫02π(9+12cos⁡θ+4cos⁡2θ) dθ. A = \frac{1}{2}\int_0^{2\pi} (3 + 2\cos\theta)^2\,d\theta = \frac{1}{2}\int_0^{2\pi} (9 + 12\cos\theta + 4\cos^2\theta)\,d\theta.

Using cos⁡2θ=1+cos⁡2θ2 \cos^2\theta = \frac{1 + \cos 2\theta}{2} , the integral yields 12(18π+4π)=11π \frac{1}{2}(18\pi + 4\pi) = 11\pi .

(b) Value of drdθ \frac{dr}{d\theta} at θ=π3 \theta = \frac{\pi}{3} :drdθ=−2sin⁡θ  ⟹  drdθ∣π/3=−2(32)=−3. \frac{dr}{d\theta} = -2\sin\theta \implies \frac{dr}{d\theta}\Big|_{\pi/3} = -2\left(\frac{\sqrt{3}}{2}\right) = -\sqrt{3}.

Since r(π/3)=3+2(1/2)=4>0 r(\pi/3) = 3 + 2(1/2) = 4 > 0 and drdθ<0 \frac{dr}{d\theta} < 0 , the distance between the curve and the origin is decreasing at θ=π3 \theta = \frac{\pi}{3} .

⚠️ AP Reader Scoring Traps & BC FRQ Conventions
  • FRQ 6 Taylor Series Template: Always memorize the 4 foundational Maclaurin series: ex e^x , sin⁡x \sin x , cos⁡x \cos x , and 11−x \frac{1}{1-x} . When asked to find series for related functions, manipulate, differentiate, or integrate term-by-term. Never recalculate derivatives from scratch unless explicitly instructed.
  • Lagrange Bound Justification: On Lagrange error bound problems, clearly identify each piece of M(n+1)!∣x−c∣n+1 \frac{M}{(n+1)!}|x-c|^{n+1} : state n n , (n+1)! (n+1)! , the interval [c,x] [c, x] , and the bound M M . Omitting the factorial or the absolute value power forfeits the point.
  • Explaining Definite Integrals in Context: When asked to 'interpret the meaning of ∫04(x′)2+(y′)2 dt \int_0^4 \sqrt{(x')^2 + (y')^2}\,dt ', you must state 3 distinct components: (1) what the value represents (total distance traveled), (2) the correct units (e.g. meters), and (3) the exact time interval (from t=0 t = 0 to t=4 t = 4 seconds).
An AP Calculus BC student scores 36 out of 45 on Section I (Multiple Choice) and 38 out of 54 on Section II (Free Response). Compute the student's composite score (scaled out of 108 total points) according to standard AP weighting (Section I = 1.20 × raw score, Section II = 1.00 × raw score).
Section I Composite=1.20×36=43.2\text{Section I Composite} = 1.20 \times 36 = 43.2. Section II Composite=1.00×38=38.0\text{Section II Composite} = 1.00 \times 38 = 38.0. Total Composite Score=43.2+38.0=81.2 out of 108\text{Total Composite Score} = 43.2 + 38.0 = 81.2\text{ out of 108} (approximately 75.2%), which comfortably qualifies for an AP score of 5 (typically requiring ~66–72 composite points depending on the exam curve).
📝 Chapter Quiz
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Exam practice

1

For x=cos⁡t, y=sin⁡t x=\cos t,\ y=\sin t , find dydx \dfrac{dy}{dx} at t=π2 t=\tfrac{\pi}{2} .

FRQ

dydx=cos⁡t−sin⁡t=−cot⁡t \dfrac{dy}{dx}=\dfrac{\cos t}{-\sin t}=-\cot t ; at t=π2 t=\tfrac{\pi}{2} , cot⁡π2=0 \cot\tfrac{\pi}{2}=0 .

dydx=0. \frac{dy}{dx}=0.
2

Does ∑n=1∞1n2 \displaystyle\sum_{n=1}^{\infty}\frac{1}{n^2} converge or diverge?

MCQ

A p p -series with p=2>1 p=2>1 , so it converges (in fact to π2/6 \pi^2/6 ).

3

Find the area enclosed by the polar curve r=2 r=2 .

FRQ

A=12∫02πr2 dθ=12∫02π4 dθ=12⋅4⋅2π=4π A=\tfrac12\displaystyle\int_0^{2\pi} r^2\,d\theta=\tfrac12\int_0^{2\pi}4\,d\theta=\tfrac12\cdot 4\cdot 2\pi=4\pi — the circle of radius 2.

4

Differentiate y=x4−3x2 y=x^4-3x^2 .

MCQ
y′=4x3−6x. y'=4x^3-6x.
5

Evaluate ∫026x2 dx \displaystyle\int_0^{2} 6x^2\,dx .

MCQ
[2x3]02=16. \big[2x^3\big]_0^{2}=16.
6

Evaluate lim⁡x→0tan⁡xx \displaystyle\lim_{x\to 0}\frac{\tan x}{x} .

MCQ
1. 1.
7

Differentiate y=ex2 y=e^{x^2} .

MCQ
y′=2x ex2. y'=2x\,e^{x^2}.
8

Evaluate ∫x ex2 dx \displaystyle\int x\,e^{x^2}\,dx .

MCQ

Let u=x2 u=x^2 , x dx=12 du x\,dx=\tfrac12\,du :

12ex2+C. \tfrac12 e^{x^2}+C.
9

Differentiate y=arctan⁡x y=\arctan x .

MCQ
y′=11+x2. y'=\frac{1}{1+x^2}.
10

Evaluate ∫11+x2 dx \displaystyle\int \frac{1}{1+x^2}\,dx .

MCQ
arctan⁡x+C. \arctan x+C.
11

Evaluate ∫x ex dx \displaystyle\int x\,e^{x}\,dx .

FRQ

By parts:

ex(x−1)+C. e^{x}(x-1)+C.
12

Evaluate ∫ln⁡x dx \displaystyle\int \ln x\,dx .

FRQ
xln⁡x−x+C. x\ln x-x+C.
13

Evaluate ∫xsin⁡x dx \displaystyle\int x\sin x\,dx .

FRQ

By parts, u=x, dv=sin⁡x dx u=x,\ dv=\sin x\,dx :

−xcos⁡x+sin⁡x+C. -x\cos x+\sin x+C.
14

Evaluate ∫1x2−1 dx \displaystyle\int \frac{1}{x^2-1}\,dx .

FRQ

Partial fractions 12(1x−1−1x+1) \tfrac12\big(\tfrac{1}{x-1}-\tfrac{1}{x+1}\big) :

12ln⁡∣x−1x+1∣+C. \tfrac12\ln\left|\frac{x-1}{x+1}\right|+C.
15

Evaluate ∫1∞1x2 dx \displaystyle\int_1^{\infty}\frac{1}{x^2}\,dx .

FRQ

Improper: [−1x]1∞=0−(−1) \big[-\tfrac1x\big]_1^{\infty}=0-(-1) :

1. 1.
16

Evaluate ∫0∞e−x dx \displaystyle\int_0^{\infty} e^{-x}\,dx .

FRQ
[−e−x]0∞=0−(−1)=1. \big[-e^{-x}\big]_0^{\infty}=0-(-1)=1.
17

Evaluate ∑n=0∞(12)n \displaystyle\sum_{n=0}^{\infty}\Big(\tfrac12\Big)^{n} .

MCQ
11−12=2. \frac{1}{1-\tfrac12}=2.
18

Evaluate ∑n=0∞(13)n \displaystyle\sum_{n=0}^{\infty}\Big(\tfrac13\Big)^{n} .

MCQ
11−13=32. \frac{1}{1-\tfrac13}=\frac32.
19

Evaluate ∑n=1∞(25)n \displaystyle\sum_{n=1}^{\infty}\Big(\tfrac25\Big)^{n} .

MCQ

First term 25 \tfrac25 , ratio 25 \tfrac25 :

2/51−2/5=23. \frac{2/5}{1-2/5}=\frac23.
20

Does ∑n=1∞1n \displaystyle\sum_{n=1}^{\infty}\frac1n converge?

MCQ

The harmonic series:

diverges. \text{diverges}.
21

Does ∑n=0∞(0.9)n \displaystyle\sum_{n=0}^{\infty}(0.9)^{n} converge, and to what?

MCQ

Geometric with ∣r∣<1 |r|<1 :

11−0.9=10. \frac{1}{1-0.9}=10.
22

Does ∑n=1∞1n \displaystyle\sum_{n=1}^{\infty}\frac{1}{\sqrt{n}} converge?

MCQ

p p -series with p=12≤1 p=\tfrac12\le 1 :

diverges. \text{diverges}.
23

Does ∑n=1∞nn+1 \displaystyle\sum_{n=1}^{\infty}\frac{n}{n+1} converge?

MCQ

Terms →1≠0 \to 1\neq 0 , so by the n n th-term test:

diverges. \text{diverges}.
24

Evaluate ∑n=0∞3(14)n \displaystyle\sum_{n=0}^{\infty} 3\Big(\tfrac14\Big)^{n} .

MCQ
31−14=4. \frac{3}{1-\tfrac14}=4.
25

For what x x does ∑n=0∞xnn! \displaystyle\sum_{n=0}^{\infty}\frac{x^n}{n!} converge?

FRQ

Ratio test: ∣xn+1∣→0<1 \big|\tfrac{x}{n+1}\big|\to 0<1 always:

all real x. \text{all real } x.
26

Write the Maclaurin series for ex e^{x} .

MCQ
ex=∑n=0∞xnn!=1+x+x22+⋯ . e^{x}=\sum_{n=0}^{\infty}\frac{x^{n}}{n!}=1+x+\tfrac{x^2}{2}+\cdots.
27

Give the first three nonzero terms of the Maclaurin series for sin⁡x \sin x .

FRQ
x−x36+x5120. x-\frac{x^3}{6}+\frac{x^5}{120}.
28

Give the first three terms of the Maclaurin series for cos⁡x \cos x .

FRQ
1−x22+x424. 1-\frac{x^2}{2}+\frac{x^4}{24}.
29

Use a two-term Maclaurin polynomial for ex e^{x} to approximate e0.1 e^{0.1} .

FRQ

ex≈1+x e^{x}\approx 1+x at x=0.1 x=0.1 :

1+0.1=1.1. 1+0.1=1.1.
30

Find the interval of convergence of ∑n=0∞xn \displaystyle\sum_{n=0}^{\infty} x^{n} .

FRQ

Geometric, converges for ∣x∣<1 |x|<1 :

(−1,1). (-1,1).
31

Find the interval of convergence of ∑n=1∞xnn \displaystyle\sum_{n=1}^{\infty}\frac{x^n}{n} .

FRQ

Ratio test gives ∣x∣<1 |x|<1 . Endpoints: x=1 x=1 diverges (harmonic), x=−1 x=-1 converges (alternating):

[−1,1). [-1,1).
32

Evaluate ∑n=1∞1n(n+1) \displaystyle\sum_{n=1}^{\infty}\frac{1}{n(n+1)} .

FRQ

Telescoping: 1n−1n+1 \tfrac1n-\tfrac{1}{n+1} :

∑n=1∞(1n−1n+1)=1. \sum_{n=1}^{\infty}\Big(\tfrac1n-\tfrac{1}{n+1}\Big)=1.
33

Does ∑n=1∞(−1)nn \displaystyle\sum_{n=1}^{\infty}\frac{(-1)^n}{n} converge?

MCQ

The alternating harmonic series satisfies the alternating series test:

converges. \text{converges}.
34

Find the radius of convergence of ∑n=0∞xn2n \displaystyle\sum_{n=0}^{\infty}\frac{x^n}{2^n} .

FRQ

Geometric in x2 \tfrac{x}{2} ; converges for ∣x2∣<1 \big|\tfrac{x}{2}\big|<1 :

R=2. R=2.
35

For x=t2, y=t3 x=t^2,\ y=t^3 , find dydx \dfrac{dy}{dx} .

MCQ
dydx=3t22t=3t2. \frac{dy}{dx}=\frac{3t^2}{2t}=\frac{3t}{2}.
36

For x=et, y=e2t x=e^{t},\ y=e^{2t} , find dydx \dfrac{dy}{dx} .

MCQ
dydx=2e2tet=2et. \frac{dy}{dx}=\frac{2e^{2t}}{e^{t}}=2e^{t}.
37

For x=t2, y=2t x=t^2,\ y=2t , find dydx \dfrac{dy}{dx} .

MCQ
dydx=22t=1t. \frac{dy}{dx}=\frac{2}{2t}=\frac1t.
38

For x=3t, y=t2−1 x=3t,\ y=t^2-1 , find dydx \dfrac{dy}{dx} .

MCQ
dydx=2t3. \frac{dy}{dx}=\frac{2t}{3}.
39

Find the arc length of x=t, y=t x=t,\ y=t for t∈[0,1] t\in[0,1] .

FRQ
L=∫0112+12 dt=2. L=\int_0^{1}\sqrt{1^2+1^2}\,dt=\sqrt2.
40

For x=t3, y=t2 x=t^3,\ y=t^2 , find dydx \dfrac{dy}{dx} at t=1 t=1 .

MCQ
2t3t2∣t=1=23. \frac{2t}{3t^2}\Big|_{t=1}=\frac23.
41

Find the speed of a particle with x=t2, y=t2 x=t^2,\ y=t^2 at t=1 t=1 .

FRQ

Speed =(2t)2+(2t)2=22 t =\sqrt{(2t)^2+(2t)^2}=2\sqrt2\,t at t=1 t=1 :

22. 2\sqrt2.
42

Convert the polar point (2,π2) \big(2,\tfrac{\pi}{2}\big) to rectangular coordinates.

MCQ

x=2cos⁡π2=0, y=2sin⁡π2=2 x=2\cos\tfrac{\pi}{2}=0,\ y=2\sin\tfrac{\pi}{2}=2 :

(0,2). (0,2).
43

Find the area enclosed by r=4 r=4 .

MCQ
12∫02π16 dθ=16π. \tfrac12\int_0^{2\pi}16\,d\theta=16\pi.
44

Convert the rectangular point (0,−3) (0,-3) to polar coordinates.

MCQ

r=3 r=3 , and the point is on the negative y y -axis:

(3,3π2). \big(3,\tfrac{3\pi}{2}\big).
45

Find the area enclosed by the cardioid r=1+cos⁡θ r=1+\cos\theta .

FRQ
12∫02π(1+cos⁡θ)2 dθ=3π2. \tfrac12\int_0^{2\pi}\big(1+\cos\theta\big)^2\,d\theta=\frac{3\pi}{2}.
46

Convert the rectangular point (1,1) (1,1) to polar coordinates.

MCQ

r=2 r=\sqrt2 , θ=arctan⁡1=π4 \theta=\arctan 1=\tfrac{\pi}{4} :

(2,π4). \big(\sqrt2,\tfrac{\pi}{4}\big).
47

Find the area enclosed by r=3 r=3 .

MCQ
12∫02π9 dθ=9π. \tfrac12\int_0^{2\pi}9\,d\theta=9\pi.
48

The polar curve r=2cos⁡θ r=2\cos\theta is a circle. Find its enclosed area.

FRQ

It is a circle of radius 1; equivalently 12∫−π/2π/24cos⁡2θ dθ \tfrac12\int_{-\pi/2}^{\pi/2}4\cos^2\theta\,d\theta :

π. \pi.
49

Solve dydx=3y \dfrac{dy}{dx}=3y with y(0)=1 y(0)=1 .

FRQ
y=e3x. y=e^{3x}.
50

Solve dydx=−2y \dfrac{dy}{dx}=-2y with y(0)=10 y(0)=10 .

MCQ

Exponential decay, k=−2 k=-2 :

y=10e−2x. y=10e^{-2x}.
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