How do you find the antiderivative of cos(πt)cos(sin(πt))dt?

1 Answer
Jan 14, 2017

1πsin(sin(πt))+C

Explanation:

Let's try to simplify the trig function within the trig function by letting u be the inside function, that is, u=sin(πt). Differentiating this shows that du=πcos(πt)dt. (Recall to use the chain rule.)

We currently have cos(πt)dt in the integral, so we need the factor of π.

cos(πt)cos(sin(πt))dt=1πcos(sin(πt))πcos(πt)dt

Substituting in:

=1πcos(u)du

This is a common integral:

=1πsin(u)+C

Substituting back in u=sin(πt):

=1πsin(sin(πt))+C