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posted by Liz Friday, November 8, 2013 at 8:18pm.

prove or disprove cos(x-y)=cos(x)-cos(y)

try x = y = 45 degrees cos (45 - 45) = cos 45 - cos 45 cos 0 = 1/sqrt2 - 1/sqrt 2 1 = 0 no way :)

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