# help solving identity simple problem

• April 22nd 2010, 01:50 PM
micbal9388
help solving identity simple problem
I'm confused at how to use identities to solve problems such as sin(2theta)sin theta = cosine theta? Another example of a problem would be sin(2 theta) = cosine theta
Can anyone help?
• April 22nd 2010, 02:09 PM
pickslides
Quote:

Originally Posted by micbal9388
I'm confused at how to use identities to solve problems such as sin(2theta)sin theta = cosine theta?

Maybe try

$\sin 2\theta \sin \theta = \cos\theta$

$2\sin \theta \cos\theta \sin \theta = \cos\theta$

$2\sin \theta \sin \theta = 1$

$2\sin ^2\theta = 1$

$\sin ^2\theta = \frac{1}{2}$

$\sin \theta = \frac{1}{\sqrt{2}}$

Can you finish it from here?