Question

A?

Answer 1

you might have made a small error with your signs

sin^2(x) = (1-cos(2x))/2

so

sin^2(x) * sin^2(x) * 2 = 2 * (1-cos(2x))/2 * (1-cos(2x))/2

= 2 * [1 - 2cos(2x) + cos^2(2x)] / 4
using our cos^2 = (1 + cos(2x))/2 identity
= 2 * [1 - 2cos(2x) + (1 + cos(4x))/2] / 4

= [2 - 4cos(2x) + 1 + cos(4x) ] / 4

(choice D not choice A)

Answer 2

D

Answer 3

because of its position on the unit circle, cos( 11pi/8 ) must be negative which is why we take the negative value not its positive, making B the better sol'n