On #2, what do you know about an isoceles triangle? If those two angles are equal, are not the sides opposite them also equal?
For #3, I think you meant: right? It looks like - 0 in what you have. Nonetheless, your method is correct, but your answers are wrong. If you add to both sides and then divide by 2, you will have:
. Now, where on your unit circle does the Your answers are where the