Question

How do you prove `cos 2x = (1-tan^2x)/(1+tan^2x)`?

Answer 1

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Explanation:

Answer 2

`cos2x=(cos^2x-sin^2x)/(cos^2x+sin^2x)=(cos^2x/cos^2x-sin^2x/cos^2x)/(cos^2x/cos^2x+sin^2x/cos^2x)=(1-tan^2x)/(1+tan^2x)`

Answer 3

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