Evaluate the indefinite integral. (Enter your answer in terms of cos function.)

so far i have:

u = 4$\displaystyle pi$t

du = $\displaystyle pi$dt

1/$\displaystyle pi$du = dt

once you subsitute it all back in i get a final answer of:

(1/$\displaystyle pi$)(cos4$\displaystyle pi$t)+c

but this is not correct....

where is my mistake?