cos^3(t) = (1-sin^2(t)) cos(t)/5
when you integrate you get sin(t)/5 -sin^3(t)/15
If you're calculating flux integrals then there is certain assumed background knowledge that you are expected to know. This thread is not the place to be revising that knowledge.
You have been given sufficient information to attempt this queston. There comes a point where you have to go ahead and calculate your answer without getting confirmation that every step is correct.