How do you use the double angle or half angle formulas to express sin x/2 in terms of cos x?

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Answer 1 · 2015-10-13T00:40:10

cos 2x = 1 - 2 #sin^2#x #=># 2#sin^2# x = 1 - cos2x #=>## sin^2#x/2 = (1- cosx ) /2#=># sin x/2 = #sqrt# 1/2(1 - cos x).