SOLUTION: Hi, I would like to start off by saying thank you for answering my question. The text book has asked to prove the identity : tan2theta = (2tantheta)/(1-tan^2theta) Your h

Question 1039980: Hi,
I would like to start off by saying thank you for answering my question.
The text book has asked to prove the identity :
tan2theta = (2tantheta)/(1-tan^2theta)
Your help is so greatly appreciated. You have no idea
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
prove the identity :
tan2theta = (2tantheta)/(1-tan^2theta)
-------
tan(2t) = sin(2t)/cos(2t)
===
= 2sin(t)cos(t)/(cos^2(t)-sin^2(t))
----------
Divide numerator and denominator by cos^2(t) to get::
-----
= 2sin(t)/cos(t) / (1-tan^2(t))
------
= 2*tan(t)/(1-tan^2(t))
QED
====================
Note:: You could find this proof online using Google.
--------------------
Cheers,
Stan H.
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