# Math Help - Cosine graphing....?

1. ## Cosine graphing....?

How do you graph $cos^2 x$?

2. Originally Posted by Bartimaeus
How do you graph $cos^2 x$?
[we use a TI-84+ in school so that's easier...]

There are several substitution formulas:

$cos^2 x + sin^2 x = 1$
$2cos^2 x - 1 = cos2 x$
$1 - 2sin^2 x = cos2x$
$cos^2 x - sin^2 x = cos2x$

If you use the second one you get
$2cos^2 x - 1 = cos2 x$
$2cos^2 x = 1 + cos2x$
$cos^2 x = 1/2 + 1/2 cos2x$

so the problem changed to how do you draw the graph of $1/2 + 1/2cos2x$

3. Ah ha! Wow, that is remarkably ... simple.
Darn trigonometric identities, grr....

Thanks!!!