Proof Help!?

**johnreal** · April 15th 2012, 02:57 PM

I have been stuck on this proof for a while, i know all the identities and think i am either really close and cant see it or my algebra is wrong.
(1-tan^2x)/(1+tan^2x)=1-2sin^2x
i have tried it from many angles, so far the only thing i am sure i did correct was
numerator: (sin^2+cos^2)-(sin^2/cos^2)
denominator: (sin^2+cos^2)+(sin^2/cos^2)

Thanks for any help in advance.

**Plato** · April 15th 2012, 03:08 PM

Originally Posted by johnreal

I have been stuck on this proof for a while, i know all the identities and think i am either really close and cant see it or my algebra is wrong.
(1-tan^2x)/(1+tan^2x)=1-2sin^2x

$\frac{{1 - {{\tan }^2}(x)}}{{1 + {{\tan }^2}(x)}} = \frac{{{{\cos }^2}(x) - {{\sin }^2}(x)}}{{{{\cos }^2}(x) + {{\sin }^2}(x)}}$

**johnreal** · April 15th 2012, 03:18 PM

Thanks i see how i would get the answer from there, i saw my algebra mistake when using the fractions, BTW cool name.

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