SOLUTION: Prove that (1-tan^2 x) / (1+tan^2 x) = cos 2 x For each step of the proof I also need to know what rule this applies to (algebra, reciprocal, quotient, Pythagorean, double angl

Question 682652: Prove that (1-tan^2 x) / (1+tan^2 x) = cos 2 x
For each step of the proof I also need to know what rule this applies to (algebra, reciprocal, quotient, Pythagorean, double angle, or sum and differences). Please state the rule after each step***
Thank you so so much for your help!
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Prove that (1-tan^2 x) / (1+tan^2 x) = cos 2 x
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(1-tan^2 x) /sec^2 = cos(2x)
(1-tan^2 x)*cos^2(x) = cos(2x)
cos^2 - sin^2 = cos(2x) Double angle formula

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