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September 21, 2014

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

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 10:41pmLS =

cos^2 B - sin^2 B

= cos^2 B - (1 - cos^2 B)

= 2cos^2 B - 1

= RS

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