Integration by Parts
\[\int u\,dv = uv - \int v\,du\]
★ LIATE rule for choosing \(u\): Logarithm · Inverse trig · Algebraic · Trig · Exponential
Trigonometric Substitution
\(\sqrt{a^2-x^2}\): let \(x=a\sin\theta\) ·
\(\sqrt{a^2+x^2}\): let \(x=a\tan\theta\) ·
\(\sqrt{x^2-a^2}\): let \(x=a\sec\theta\)
Partial Fractions
Decompose rational \(\dfrac{P(x)}{Q(x)}\) into sums of simpler fractions, matching degree of numerator < denominator.
Worked Example
Evaluate \(\displaystyle\int x\,e^x\,dx\).
Let \(u=x\), \(dv=e^x dx\) → \(du=dx\), \(v=e^x\).
\(\displaystyle\int x e^x dx = xe^x - \int e^x dx = xe^x - e^x + C = e^x(x-1)+C\)
✓ Answer: \(e^x(x-1)+C\)
IBPTrig SubPartial Fractions