I have two problems for homework tonight that I can't get.

they are over double and half angles.

if someone can get any of these, and show how they did it or give a short explanation how, that would be awesome.

1. sin2x[4cos^4(x) - 4cos^2(x)]^2

I started by changing sin2x to 2sinxcosx & squared the parenthetical part

then I multiplied it all out but I don't see any way to simplify.

2. sin(C + D) = 7/8, (C+D) is in quadrant I, and sin C = 2/8, C is in quadrant I

find sin D

this one I'm rather lost. I know the formula for sin(C + D), so I can make it

(sinC)(cosD) + (cosC)(sinD) = 7/8

change the sin C to 2/8... but can't get it all figured out.

please help!