Im still trying to wrap my head around the last one. But heres another im having trouble with : cos theta sine^6 theta
Again, make a substitution $\displaystyle u=sin\theta \rightarrow du=cos\theta d\theta$. Substitute into the integral and you will now have:
$\displaystyle \int u^6 \,du$.
Integrate from here and substitute u back in and then you'll have your answer! Hope this helped you out!