Electrical engineering question?

Question

The current entering the upper terminal of an unspecified basic circuit element is

i = 20 cos 5000t Amps

Assume the charge at the upper terminal is zero at the instant the current is passing through its maximum value. Find the expression for q(t).

I know I have to integrate, but I'm not getting the answer the book gave me.

Answer 1

i = 20 cos 5000t Amps
q(0) = 0
q = 20∫cos(5,000t)dt
q = (2/500)sin(5,000t)
q = 0.004sin(5,000t)