# derive identity help

• Nov 20th 2008, 08:48 PM
jvignacio
derive identity help
$\displaystyle \frac{\cos\theta\tan\theta + \sin\theta}{\tan\theta} = 2\cos\theta$

help deriving this identity. thank you
• Nov 20th 2008, 08:51 PM
Chris L T521
Quote:

Originally Posted by jvignacio
$\displaystyle \frac{\cos\theta\tan\theta + \sin\theta}{\tan\theta} = 2\cos\theta$

help deriving this identity. thank you

Note that $\displaystyle \cos\vartheta\tan\vartheta=\sin\vartheta$ and $\displaystyle \tan\vartheta=\frac{\sin\vartheta}{\cos\vartheta}$

Can you try and see if you can establish this identity?

--Chris
• Nov 20th 2008, 10:08 PM
jvignacio
Quote:

Originally Posted by Chris L T521
Note that $\displaystyle \cos\vartheta\tan\vartheta=\sin\vartheta$ and $\displaystyle \tan\vartheta=\frac{\sin\vartheta}{\cos\vartheta}$

Can you try and see if you can establish this identity?

--Chris

no im not very familiar with identities :(
• Nov 21st 2008, 09:54 AM
Krizalid
Those are basic ones, better you review some of trig.
• Nov 21st 2008, 10:06 AM
Math_Helper