SOLUTION: Prove that {{{ Cos^4A - Sin^4A = 1 - 2Sin^2A }}}

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Question 495314: Prove that
+Cos%5E4A+-+Sin%5E4A+=+1+-+2Sin%5E2A+
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
Prove:
Cos^4A - Sin^4A = 1 - 2Sin^2A
Starting with left side
cos^4-sin^4
=(cos^2+sin^2)(cos^2-sin^2)
=(cos^2+sin^2)(1-sin^2-sin^2)
=1(1-2sin^2)
=1-2sin^2
verified:
left side = right side