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trig function

cos^2(x)=1+cos(2x) / 2

HELP PLEASE THANKS

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  1. in your previous post we just proved:
    cos (2x) = cos^2 x - sin^2 x
    but sin^2 x = 1 - cos^2 x
    so
    cos (2x) = cos^2 x - (1 - cos^2 x)
    = 2 cos^2 x - 1
    2cos^2 x = 1 + cos(2x)
    cos^2 x = (1 + cos(2x) )/2

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