Mistake Master

AP Calculus BC Reference

Unlike AP Physics or AP Statistics, the AP Calculus exam provides no formula sheet: every derivative rule, theorem statement, integral form, and series fact below has to come from memory. This page collects what is worth knowing cold for AP Calculus BC, organized by family, with the BC-only material tagged so AB review stays separable. These are the standard results, not an official College Board document; confirm the exam's exact provided materials and calculator policy on AP Central. Taking AB? The AB reference is this page without the BC-only layer. Every entry links to the unit where Mistake Master teaches and drills it.

Units 1-2

Limits and Continuity

What a limit claims, when a function is continuous, and how the derivative is born as a limit. Where it slips: answering with the function's value at a point when the question asks for the limit, and citing the IVT without first stating that the function is continuous.

$$ f'(a) = \lim_{h \to 0} \dfrac{f(a+h) - f(a)}{h} = \lim_{x \to a} \dfrac{f(x) - f(a)}{x - a} $$

Limit definition of the derivative

Both forms appear on the exam, usually in disguise: a limit shaped like either one IS a derivative, and recognizing which function and which point beats grinding out the algebra.

Unit 2 · Topics 2.1-2.2
$$ \lim_{x \to a^-} f(x) = \lim_{x \to a^+} f(x) = f(a) $$

Continuity at a point

Three requirements: the limit exists (left agrees with right), the function value is defined, and the two match. A jump, a hole, and a relocated point each break a different one.

Unit 1 · Topic 1.11
$$ f \text{ continuous on } [a,b] \Rightarrow f \text{ attains every value between } f(a) \text{ and } f(b) $$

Intermediate Value Theorem

Guarantees a value is reached somewhere in the interval; it never locates it. State continuity on the closed interval before invoking it, since that hypothesis is the whole theorem.

Unit 1 · Topic 1.16
$$ \text{differentiable} \Rightarrow \text{continuous}, \quad \text{converse false} $$

Differentiability and continuity

Differentiability is the stronger condition. The absolute value function is continuous everywhere yet not differentiable at zero: corners, cusps, and vertical tangents all survive continuity.

Unit 2 · Topic 2.4
Units 2-4

Derivative Rules

The differentiation toolkit, from the power rule to L'Hospital. Where it slips: the forgotten inner derivative in the chain rule, and the order of the quotient rule's numerator.

$$ \dfrac{d}{dx}\,x^n = n\,x^{\,n-1} $$

Power rule

Works for every real exponent. Rewrite roots and reciprocals as powers before differentiating; the square root of x is x to the one half.

Unit 2 · Topic 2.5
$$ (u\,v)' = u'\,v + u\,v' $$

Product rule

Each factor takes a turn being differentiated while the other rides along. The derivative of a product is NOT the product of the derivatives.

Unit 2 · Topic 2.8
$$ \left( \dfrac{u}{v} \right)' = \dfrac{u'\,v - u\,v'}{v^2} $$

Quotient rule

The numerator's order matters: derivative of the top times the bottom comes first. Swapping the two terms flips the sign of every answer.

Unit 2 · Topic 2.9
$$ \dfrac{d}{dx}\,f\big(g(x)\big) = f'\big(g(x)\big) \cdot g'(x) $$

Chain rule

Differentiate the outer function at the inner one, then multiply by the inner derivative. That trailing factor is the single most dropped item in the course.

Unit 3 · Topic 3.1
$$ (\sin x)' = \cos x, \quad (\cos x)' = -\sin x, \quad (\tan x)' = \sec^2 x $$

Trig derivatives

Also: secant gives secant times tangent, cotangent gives negative cosecant squared, cosecant gives negative cosecant times cotangent. Every co-function carries the minus sign.

Unit 2 · Topics 2.7, 2.10
$$ (e^x)' = e^x, \quad (a^x)' = a^x \ln a, \quad (\ln x)' = \dfrac{1}{x} $$

Exponential and log derivatives

The power rule needs a constant exponent, so a to the x is not x times a to the x minus 1. For other log bases, divide: log base a of x differentiates to 1 over x ln a.

Unit 2 · Topic 2.7
$$ (\arcsin x)' = \dfrac{1}{\sqrt{1 - x^2}}, \quad (\arctan x)' = \dfrac{1}{1 + x^2} $$

Inverse trig derivatives

Arccosine's derivative is the negative of arcsine's. The square root marks arcsine and arccosine; the plain quadratic marks arctangent.

Unit 3 · Topic 3.4
$$ \dfrac{d}{dx}\,y^2 = 2y\,\dfrac{dy}{dx} $$

Implicit differentiation

Every y is a function of x, so each y term emits a dy/dx by the chain rule. Differentiate both sides, collect the dy/dx terms, and solve.

Unit 3 · Topic 3.2
$$ \big(f^{-1}\big)'(b) = \dfrac{1}{f'\big(f^{-1}(b)\big)} $$

Derivative of an inverse function

Evaluate the original derivative at the inverse's output: the x whose image is b, not at b itself. Reading the wrong input is where nearly every miss on this rule comes from.

Unit 3 · Topic 3.3
$$ \lim \dfrac{f(x)}{g(x)} = \lim \dfrac{f'(x)}{g'(x)} \quad \text{only for } \tfrac{0}{0} \text{ or } \tfrac{\infty}{\infty} $$

L'Hospital's rule

Verify and state the indeterminate form before applying it; on the FRQ that verification earns the point. Differentiate the top and bottom separately, never with the quotient rule.

Unit 4 · Topic 4.7
Unit 5

Theorems

The guarantee theorems: each trades hypotheses for a conclusion. Where it slips: quoting the conclusion without checking, or writing down, the hypotheses that earn it.

$$ f'(c) = \dfrac{f(b) - f(a)}{b - a} \; \text{ for some } c \text{ in } (a,b) $$

Mean Value Theorem

Somewhere, the instantaneous rate equals the average rate. Requires continuity on the closed interval and differentiability on the open interval; both belong in the justification.

Unit 5 · Topic 5.1
$$ f(a) = f(b) \Rightarrow f'(c) = 0 \; \text{ for some } c \text{ in } (a,b) $$

Rolle's Theorem

The MVT with equal endpoint values, so the guaranteed slope is zero. Same hypotheses: continuous on the closed interval, differentiable on the open one.

Unit 5 · Topic 5.1
$$ f \text{ continuous on } [a,b] \Rightarrow f \text{ attains an absolute max and min} $$

Extreme Value Theorem

A continuous function on a closed interval must reach a largest and a smallest value. Open intervals and discontinuities void the guarantee.

Unit 5 · Topic 5.2
$$ \text{compare } f \text{ at critical points and endpoints} $$

Candidates test

On a closed interval, absolute extrema live only at critical points or endpoints. Evaluate the function itself at each candidate and compare; the derivative's sign is not the finish line.

Unit 5 · Topic 5.5
Unit 6

Integrals and the FTC

Antiderivatives, substitution, and the theorem that ties accumulation to rate. Where it slips: bounds left in terms of x after a u-substitution, and the dropped absolute value on the log.

$$ \int x^n \, dx = \dfrac{x^{\,n+1}}{n+1} + C \quad (n \neq -1) $$

Antiderivative power rule

Raise the exponent, then divide by the new exponent. The excluded case is exactly the one with its own rule: the antiderivative of 1 over x is ln of the absolute value of x, plus C.

Unit 6 · Topic 6.8
$$ \int e^x \, dx = e^x + C, \quad \int \cos x \, dx = \sin x + C, \quad \int \sin x \, dx = -\cos x + C $$

Core antiderivatives

Also: secant squared integrates to tangent. The minus sign lives on the integral of sine, not of cosine; differentiating your answer takes five seconds and catches the swap.

Unit 6 · Topic 6.8
$$ \int \dfrac{dx}{1 + x^2} = \arctan x + C, \quad \int \dfrac{dx}{\sqrt{1 - x^2}} = \arcsin x + C $$

Inverse trig antiderivatives

The derivative table read backward. The square root goes with arcsine; the plain quadratic goes with arctangent.

Unit 6 · Topic 6.8
$$ \int f\big(g(x)\big)\,g'(x)\,dx = \int f(u)\,du, \quad u = g(x) $$

u-substitution

The chain rule run in reverse: the integrand must contain the inner function's derivative, up to a constant. On a definite integral, convert the bounds to u-values too.

Unit 6 · Topic 6.9
$$ \dfrac{d}{dx} \int_a^x f(t)\,dt = f(x) $$

FTC, part 1

The derivative of an accumulation function is the integrand, evaluated at the upper limit. If the upper limit is g(x), the chain rule appends a factor of g'(x).

Unit 6 · Topic 6.4
$$ \int_a^b f(x)\,dx = F(b) - F(a) $$

FTC, part 2

Any antiderivative F evaluates the definite integral: upper minus lower. Net change of F equals the integral of its rate, which is how most applied FRQ parts are set up.

Unit 6 · Topic 6.7
$$ f_{\text{avg}} = \dfrac{1}{b - a} \int_a^b f(x)\,dx $$

Average value

The average of a function over an interval is the integral divided by the interval's length. It is not the average of the endpoint values.

Unit 8 · Topic 8.1
$$ \int_a^b f = -\int_b^a f, \qquad \int_a^b f = \int_a^c f + \int_c^b f $$

Definite integral properties

Reversing the bounds flips the sign; the interval splits at any point between. Constants factor out and sums split term by term, but products and quotients do not.

Unit 6 · Topic 6.6
Unit 6

Integration Techniques BC only

The three techniques BC adds to the antidifferentiation toolkit. Where it slips: choosing u and dv so the new integral is harder than the old one, and treating a divergent improper integral as if it had a value.

$$ \int u \, dv = uv - \int v \, du $$

Integration by parts BC only

The product rule run in reverse. Pick u to get simpler when differentiated (logs and inverse trig first) and dv to be something you can integrate; the goal is an easier integral, not just a different one.

Unit 6 · Topic 6.11
$$ \dfrac{px + q}{(x - a)(x - b)} = \dfrac{A}{x - a} + \dfrac{B}{x - b} $$

Linear partial fractions BC only

A rational function with a factorable denominator splits into pieces that each integrate to a logarithm. BC keeps to distinct linear factors, so this template is the whole technique.

Unit 6 · Topic 6.12
$$ \int_a^{\infty} f(x)\,dx = \lim_{b \to \infty} \int_a^b f(x)\,dx $$

Improper integrals BC only

Write the limit explicitly; the integral converges only if the limit is finite. The same move handles an integrand that blows up at an endpoint of the interval.

Unit 6 · Topic 6.13
Units 4, 8

Applications

Area, volume, and motion. Where it slips: squaring the difference of the radii instead of subtracting their squares, and reporting displacement when the question asks for total distance.

$$ A = \int_a^b \big[ f(x) - g(x) \big] \, dx $$

Area between curves

Top minus bottom when integrating in x; right minus left when integrating in y. If the curves cross, split the integral at the intersection so the difference stays positive.

Unit 8 · Topics 8.4-8.6
$$ V = \pi \int_a^b \big[ r(x) \big]^2 \, dx $$

Disc method

Each slice is a solid circle whose radius runs from the axis of revolution to the curve. Revolving around a shifted axis changes the radius, not the formula.

Unit 8 · Topics 8.9-8.10
$$ V = \pi \int_a^b \left( R^2 - r^2 \right) dx $$

Washer method

Subtract the squares: outer radius squared minus inner radius squared. Squaring the difference of the radii is a different, wrong number.

Unit 8 · Topics 8.11-8.12
$$ V = \int_a^b A(x) \, dx $$

Volume by cross sections

Integrate the area of the slice. The region gives each slice's base length; feed that length into the shape's own area formula, halving the base first for a semicircle's radius.

Unit 8 · Topics 8.7-8.8
$$ v(t) = s'(t), \quad a(t) = v'(t), \quad \text{speed} = |v(t)| $$

Motion along a line

Velocity is the derivative of position, acceleration of velocity. Speed is the absolute value of velocity, and a particle speeds up exactly when velocity and acceleration share a sign.

Unit 4 · Topic 4.2
$$ \Delta s = \int_{t_1}^{t_2} v(t)\,dt, \qquad \text{distance} = \int_{t_1}^{t_2} \big| v(t) \big| \, dt $$

Displacement vs. total distance

Integrating velocity gives net change in position; integrating speed gives ground covered. They differ whenever the particle turns around, which is exactly when exams ask.

Unit 8 · Topic 8.2
$$ L = \int_a^b \sqrt{1 + \big[ f'(x) \big]^2} \, dx $$

Arc length BC only

Square the derivative before adding the 1, and keep everything under the root. The parametric version in Unit 9 uses the same idea with both coordinate derivatives.

Unit 8 · Topic 8.13
Unit 7

Differential Equations

Separating variables, plus the two BC additions: Euler's method and the logistic model. Where it slips: applying the initial condition after sloppy exponentiation instead of right after integrating, and reading the logistic equation's fastest growth at the carrying capacity instead of half of it.

$$ \dfrac{dy}{dx} = f(x)\,g(y) \;\Rightarrow\; \int \dfrac{dy}{g(y)} = \int f(x)\,dx $$

Separation of variables

Move every y to one side and every x to the other before integrating; a stray factor left behind poisons both integrals. One constant of integration, applied immediately, is enough.

Unit 7 · Topics 7.6-7.7
$$ \dfrac{dy}{dt} = ky \;\Rightarrow\; y = y_0\,e^{kt} $$

Exponential growth and decay

Rate proportional to amount forces this solution: initial value y-zero, growth for positive k, decay for negative k. Recognize the differential equation and skip the re-derivation.

Unit 7 · Topic 7.8
$$ y_{n+1} = y_n + f(x_n, y_n)\,\Delta x $$

Euler's method BC only

Step along tangent lines: each new y is the old y plus slope times step, with the slope recomputed from the differential equation at each new point, never reused.

Unit 7 · Topic 7.5
$$ \dfrac{dy}{dt} = ky \left( 1 - \dfrac{y}{L} \right) $$

Logistic model BC only

Solutions approach the carrying capacity L without crossing it, and growth is fastest when y equals L over 2. Both facts are read off the equation, no solving required.

Unit 7 · Topic 7.9
Unit 9

Parametric, Polar, and Vector BC only

Motion in the plane and curves that are not functions of x. Where it slips: flipping the quotient in dy/dx, and dropping the one half in polar area.

$$ \dfrac{dy}{dx} = \dfrac{dy/dt}{dx/dt} $$

Parametric slope BC only

The y-derivative goes on top, and the expression is defined where dx/dt is not zero. A vertical tangent appears where dx/dt vanishes while dy/dt does not.

Unit 9 · Topic 9.1
$$ \dfrac{d^2y}{dx^2} = \dfrac{\frac{d}{dt}\!\left[ \frac{dy}{dx} \right]}{dx/dt} $$

Parametric second derivative BC only

Differentiate dy/dx with respect to t, then divide by dx/dt again. It is NOT the ratio of the second derivatives of y and x.

Unit 9 · Topic 9.2
$$ \text{speed} = \sqrt{ \left( \dfrac{dx}{dt} \right)^2 + \left( \dfrac{dy}{dt} \right)^2 } $$

Speed of a vector-valued motion BC only

The magnitude of the velocity vector. In two dimensions, speed is no longer an absolute value; it is a Pythagorean length of both component rates.

Unit 9 · Topics 9.4-9.6
$$ L = \int_{t_1}^{t_2} \sqrt{ \left( \dfrac{dx}{dt} \right)^2 + \left( \dfrac{dy}{dt} \right)^2 } \, dt $$

Parametric arc length BC only

Distance traveled is the integral of speed: the same integrand as the speed formula. This one formula answers both arc length and total distance questions in Unit 9.

Unit 9 · Topic 9.3
$$ A = \dfrac{1}{2} \int_{\alpha}^{\beta} r^2 \, d\theta $$

Polar area BC only

The one half is part of the formula, not optional. Between two curves, use one half the integral of outer r squared minus inner r squared over the shared angle interval.

Unit 9 · Topics 9.8-9.9
$$ x = r\cos\theta, \quad y = r\sin\theta, \quad \dfrac{dy}{dx} = \dfrac{dy/d\theta}{dx/d\theta} $$

Polar slope BC only

Convert to x and y first, then take the parametric quotient with theta as the parameter. The derivative dr over d-theta alone is not a slope on the graph.

Unit 9 · Topic 9.7
Unit 10

Infinite Series BC only

Convergence tests, error bounds, and the Taylor machinery. Where it slips: using the nth term test to prove convergence, and skipping the endpoint check on an interval of convergence.

$$ \sum_{n=0}^{\infty} a\,r^{\,n} = \dfrac{a}{1 - r} \quad \text{when } |r| \lt 1 $$

Geometric series BC only

Converges exactly when the ratio's absolute value is below 1, to first term over 1 minus r. The a in the numerator is the first term actually present, whatever the starting index.

Unit 10 · Topic 10.2
$$ \lim_{n \to \infty} a_n \neq 0 \;\Rightarrow\; \sum a_n \text{ diverges} $$

nth term test BC only

A divergence test only. Terms going to zero proves nothing: the harmonic series is the standing counterexample, terms shrinking to zero while the sum diverges.

Unit 10 · Topic 10.3
$$ \sum_{n=1}^{\infty} \dfrac{1}{n^p} \; \text{ converges} \iff p \gt 1 $$

p-series BC only

Convergence needs p strictly greater than 1. The boundary case p equals 1 is the harmonic series, which diverges.

Unit 10 · Topic 10.5
$$ \text{integral, comparison, limit comparison, alternating, ratio} $$

The convergence tests BC only

Know each by name; the FRQ asks you to cite the one you used. Ratio test: below 1 converges absolutely, above 1 diverges, exactly 1 says nothing and another test must finish the job.

Unit 10 · Topics 10.4-10.9
$$ \big| S - S_n \big| \le a_{n+1} $$

Alternating series error bound BC only

For an alternating series whose terms decrease in magnitude to zero, the error after n terms is at most the magnitude of the first omitted term. It applies only to alternating series.

Unit 10 · Topic 10.10
$$ P_n(x) = \sum_{k=0}^{n} \dfrac{f^{(k)}(a)}{k!}\,(x - a)^k $$

Taylor polynomial BC only

Centered at a; Maclaurin means a equals 0. The kth coefficient is the kth derivative at the center divided by k factorial, and that division is the most dropped piece.

Unit 10 · Topic 10.11
$$ e^x = \sum_{n=0}^{\infty} \dfrac{x^n}{n!}, \quad \sin x = \sum_{n=0}^{\infty} \dfrac{(-1)^n x^{2n+1}}{(2n+1)!}, \quad \cos x = \sum_{n=0}^{\infty} \dfrac{(-1)^n x^{2n}}{(2n)!} $$

Standard Maclaurin series BC only

Sine takes the odd powers, cosine the even; all three converge for every x. The fourth to memorize: 1 over 1 minus x is the sum of x to the n, valid only for absolute value of x below 1.

Unit 10 · Topic 10.14
$$ \big| R_n(x) \big| \le \dfrac{M \, |x - a|^{\,n+1}}{(n+1)!} $$

Lagrange error bound BC only

M is a bound on the absolute value of the next derivative, the (n+1)st, on the interval between a and x. It bounds the error of any Taylor polynomial, alternating or not.

Unit 10 · Topic 10.12
$$ \lim_{n \to \infty} \left| \dfrac{a_{n+1}}{a_n} \right| \lt 1 $$

Radius and interval of convergence BC only

The ratio test applied to a power series yields the radius. The endpoints always come back inconclusive from the ratio test, so each must be tested separately with another test.

Unit 10 · Topic 10.13

Knowing the formula is not the same as not slipping on it

Most AP Calculus points are lost to a small set of predictable reasoning errors, not to forgotten formulas. Mistake Master diagnoses which ones are costing you points, then drills only those.

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