1. ## multiple angles

$cos\frac {x}{4} = 0$

What do I do here?
And how do I know when to use $2n\pi$ or $n\pi$

2. Originally Posted by >_<SHY_GUY>_<
$cos\frac {x}{4} = 0$

What do I do here?
And how do I know when to use $2n\pi$ or $n\pi$
you should know where $\cos(u) = 0$ from your knowledge of the unit circle ...

$\frac{x}{4} = \frac{\pi}{2} \, , \, \frac{3\pi}{2} \, , \, \frac{5\pi}{2} \, , \, ...$