SOLUTION: Verify that (1-tanx)/(1+tanx)= 2cos^2x-1

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Question 976153: Verify that
(1-tanx)/(1+tanx)= 2cos^2x-1
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
There must be a typo, but I cannot guess what it should be.
%281-tan%28x%29%29%2F%281%2Btan%28x%29%29=2cos%5E2%28x%29-1 is not true for all values of x .
For example, for the angle shown here ,
cos%28red%28x%29%29=4%2F5=0.8 , sin%28red%28x%29%29=3%2F5=0.6%29 , and tan%28red%28x%29%29=3%2F4=0.75 .
In that case,
(rounded), and
2cos%5E2%28red%28x%29%29-1=2%2A0.8%5E2-1=2%2A0.64-1=1.28-1=0.28