I'm about done all my homework for this unit, but I seem to be stuck on my last 2 questions....any help would really be appreciated.

Solve each equation:

a) 2cos^2x + 3cosx -2 = 0

and

b) sinx = cos2x

My lesson book is not very good on explaining the process of solving for x and provided very few examples....which is why I'm stuck. I just want to hand in my homework tonight and worry about understanding it when I can actually ask the teacher for help (which won't be until Monday)

Thank you for any help you can give me!