Once again, I need help on some trigonometric equations.

If cos(x)=-3/5, and pi/2 < x < 3pi/2, find sin(x/2)

Rewrite as product: sin3y-sin4y

If sin2x-cosx=0, find all the solutions in the interval [0, 2pi).

Thanks.

(If I don't respond it's because I've fallen asleep)