1. ## [SOLVED] trig identities

i havent posted in a while, but i need some help in homework.

$\displaystyle cos^x - sin^2x = 1 - 2sin^2x$

i have a feeling that it involves one of the pythagorean identities, but i may be wrong.

2. Before going forward are you absolutely certain the problem has been written correctly?

3. Originally Posted by ANDS!
Before going forward are you absolutely certain the problem has been written correctly?
sorry, i took note that i wrote it incorrectly, its supposed to be:

$\displaystyle cos^2x$

4. Ok well that makes a lot more sense. This one is fairly easy and you may well kick yourself. Remember that $\displaystyle cos^{2}(x)$ is equal to $\displaystyle 1-sin^{2}(x)$. From there it is elementary my dear Watson.

5. Originally Posted by ANDS!
Ok well that makes a lot more sense. This one is fairly easy and you may well kick yourself. Remember that $\displaystyle cos^{2}(x)$ is equal to $\displaystyle 1-sin^{2}(x)$. From there it is elementary my dear Watson.
i see my mistake, but thank you for your help sherlock
haha