# Math Help - writing in terms of theta

1. ## writing in terms of theta

I'm not sure how to do this one.

2. Originally Posted by Neverending

I'm not sure how to do this one.
$x=3\sin(\theta) \implies \sin(\theta)=\frac{x}{3}$

Using the pythagorean theorem we get the unknown side of the triangle as $\sqrt{9-x^2}$

So we get that

$\cos(\theta) =\frac{\sqrt{9-x^2}}{3} \implies \sqrt{9-x^2}=3\cos(\theta)$

3. wow i've never done something like this before. Thanks for showing me the method!