Integral cos^4(x)dx?

Question

i know i have to use integration by parts but i'm not quite sure how to go about it

Answer 1

Split into cos^3(x) and cos(x). Set u=cos^3(x) and dv=cos(x)

That leaves an integral sin(x)cos^3(x), to integrate use substitution with u=cos(x) to leave an integral of 3u^3 du.