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

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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 sin²(x) + cos²(x) = 1 to write 1/2 × cos(2x) in terms of sin²(x).

Penny

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