Homework Help: Pre-Cal

Posted by Hannah on Saturday, February 27, 2010 at 10:38pm.

1) Verify the identity

cos^2 B - sin^2 B = 2 cos^2 B -1

I know that cos^2 B - sin^2 B = 2 cos^2 B -1 by the double angle formula but I do not know how to show this.

Pre-Cal - Reiny, Saturday, February 27, 2010 at 10:41pm
LS =
cos^2 B - sin^2 B
= cos^2 B - (1 - cos^2 B)
= 2cos^2 B - 1
= RS

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