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Code Scholars Tutoring · AP Calculus AB

Basic antiderivatives and substitution

Unit 6 · Topics 6.8, 6.9. Original AP Calculus AB notes, worked example, and self-check.

Understand the idea

Antidifferentiation reverses derivative rules and includes an arbitrary constant. The power rule for integration excludes exponent −1\displaystyle -1, which produces a logarithm. Substitution matches a composite expression with its derivative. For definite integrals either change both bounds into the new variable or substitute back before evaluating; never mix transformed variables with original bounds. Other useful reverse patterns are ∫csc⁡2x dx=−cot⁡x+C\displaystyle \int\csc^2x\,dx=-\cot x+C and ∫csc⁡xcot⁡x dx=−csc⁡x+C\displaystyle \int\csc x\cot x\,dx=-\csc x+C. For an inverse-sine pattern, ∫dx/a2−x2=arcsin⁡(x/a)+C\displaystyle \int dx/\sqrt{a^2-x^2}=\arcsin(x/a)+C when a>0\displaystyle a>0 and ∣x∣<a\displaystyle |x|<a.

∫xn dx=xn+1n+1+C(n≠−1)∫u′u dx=ln⁡∣u∣+C∫ex dx=ex+C∫sin⁡x dx=−cos⁡x+C∫cos⁡x dx=sin⁡x+C∫sec⁡2x dx=tan⁡x+C∫sec⁡xtan⁡x dx=sec⁡x+C\begin{aligned}\int x^n\,dx&=\frac{x^{n+1}}{n+1}+C\quad(n\ne-1)\\\int\frac{u'}{u}\,dx&=\ln|u|+C\\\int e^x\,dx&=e^x+C\\\int\sin x\,dx&=-\cos x+C\\\int\cos x\,dx&=\sin x+C\\\int\sec^2x\,dx&=\tan x+C\\\int\sec x\tan x\,dx&=\sec x+C\end{aligned}

Worked example

Evaluate ∫012xex2 dx\displaystyle \int_0^1 2x e^{x^2}\,dx.

Let u=x2\displaystyle u=x^2, so du=2x dx\displaystyle du=2x\,dx. The bounds become 0\displaystyle 0 and 1\displaystyle 1. The integral is ∫01eu du=e−1\displaystyle \int_0^1e^u\,du=e-1. Differentiation of ex2\displaystyle e^{x^2} checks the antiderivative.

Try it yourself

Find ∫3x2/(x3+5) dx\displaystyle \int 3x^2/(x^3+5)\,dx.

Show solution and reasoning

With u=x3+5\displaystyle u=x^3+5, the result is ln⁡∣x3+5∣+C\displaystyle \ln|x^3+5|+C on any interval avoiding the denominator zero.