Inactive Tutor answered • 02/05/18
Tutor
New to Wyzant
Let 2a = x
We know cos 2x = cos2x - sin2x ...[well known double angle formula]
now substitute for x, and you have it!
Debbie D.
asked • 02/05/18establish the identity
cos2 2a- sin2 2a= cos 4a
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