# Thread: Pre-Calc

1. ## Pre-Calc

cos(3x+Pie)=Radical 2/2

Sorry i dont know how to do the signs...

Thank you.

2. Originally Posted by ep78
cos(3x+Pie)=Radical 2/2

Sorry i dont know how to do the signs...

Thank you.
from the unit circle (with which you should be familiar) ...

$\displaystyle \cos\left(\frac{\pi}{4}\right) = \cos\left(\frac{5\pi}{4}\right) = \frac{\sqrt{2}}{2}$

so ... $\displaystyle 3x + \pi =$ ?