How to prove?

$\displaystyle cos 2x + cos x = sin^2 x$

All Ive got so far is $\displaystyle cos^2 x - sin^2 x + cos x = sin^2 x$

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- Mar 11th 2011, 10:19 AMCritter314Equation
How to prove?

$\displaystyle cos 2x + cos x = sin^2 x$

All Ive got so far is $\displaystyle cos^2 x - sin^2 x + cos x = sin^2 x$ - Mar 11th 2011, 10:23 AMemakarov
Let's see, cos(2 * 0) + cos(0) = 2. Hmm...

- Mar 11th 2011, 10:36 AMTheChaz
It should read "solve", and we've already addressed this (7 minutes ago) at mymathforum!

I'm ok with you replying in either place... Obviously ;) - Mar 11th 2011, 06:40 PMProve It
Now substitute $\displaystyle \displaystyle \sin^2{x} = 1 - \cos^2{x}$ to get a quadratic equation in $\displaystyle \displaystyle \cos{x}$, which you will be able to solve.

- Mar 12th 2011, 03:54 PMTheChaz
Yeah, I said that already! ;)