Porisma

A hint to get started

Product-to-sum before integration

Given 2cos⁡Asin⁡B=sin⁡(A+B)−sin⁡(A−B)2\cos A\sin B=\sin(A+B)-\sin(A-B), find ∫cos⁡4θsin⁡2θ dθ\displaystyle\int\cos4\theta\sin2\theta\,d\theta.

CJC · Discussion · Question 12

Use the supplied identity with A=4θ and B=2θ before integrating.

Read the worked solution