4sinacosacos2a=sin4a.

Question

4sinacosacos2a=sin4a.

---

Answer 1

4sinα*cosα*cos2α=sin4α

4sinα*cosα*cos2α=2*(2*sinα*cosα)*cos2α=2*sin2α*cos2α=sin(2*2α)=sin4α

sin4α=sin4α