# Math Help - simplify

1. ## simplify

how do i simplify this:
(sin^2(a)+2cos(a)-1)
and make it into
(2cos(a)-cos^2(a))

2. ## Re: simplify

use $\sin^2{\theta}+\cos^2{\theta}=1$

3. ## Re: simplify

how do i get cos^2?
i only got sin^2

4. ## Re: simplify

From the given identity(in post #2) of course. use it to define sin^2 using cos^2. Come on, can't be more helpful

5. ## Re: simplify

wow, i still can't get it, can you elaborate please

6. ## Re: simplify

Originally Posted by ahmedb
wow, i still can't get it, can you elaborate please
Surely if \displaystyle \begin{align*} \sin^2{\theta} + \cos^2{\theta} \equiv 1 \end{align*} then \displaystyle \begin{align*} \sin^2{\theta} \equiv 1 - \cos^2{\theta} \end{align*}

Substitute this in place of \displaystyle \begin{align*} \sin^2{\theta} \end{align*}.

You've asked very similar questions in about four different threads, surely you have learnt something by now...

yes i did