Question from katelyne, a student:

Hello there.. I was assigned a problem that I am having trouble with in my Pre-Calc class and it is as follows:

sin^2x=1/2(1-cos2x)

Thanks! katelyne

Hi Katelyne,

Use the expression

cos(A + B) = cos(A) cos(B) - sin(A) sin(B)

with A = B = x and then use sin^{2}(x) + cos^{2}(x) = 1 to write 1/2 × cos(2x) in terms of sin^{2}(x).

Penny