Simplify please?

Question

#2cos^2(x/2)-1#

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Answer 1 · 2017-12-03T18:31:55

Use a double angle formula for cosine.

#cos(2A) = cos^2A-sin^2A#

# = 2cos^2A - 1#

So

#2cos^2(x/2)-1 = cos(2(x/2)) = cosx#