evaluate the indefinite integral:

Question

x^13(cos(x^7))dx

I've tried using integration by parts but I haven't ssem to be getting the right answer. I've used u=x^13 and dv=cos(x^7) and vice versa...

much help is appreciated

Answer 1

Let x^7 = u
7 x^6 dx = du
The integral becomes.
(integral of)(1/7) u cos u du

Perform that integration by parts, which is a lot easier, and then substitute back x^7 for u.