Question 995712
prove the following identities 
1-tan^2x/1+tan^2x = cos^2(x)-sin^2x
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Note:: 1+tan^2(x) = sec^2(x)
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Substitute to get:
(1-tan^2)/sec^2 = cos^2 - sin^2
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Multiply thru by sec^2 to get:
1-tan^2 = 1-tan^2
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Cheers,
Stan H.
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