# Math Help - Trig Identity question

1. ## Trig Identity question

I solved this and I got -n for both a) and b) . Am I just tired and can't do math any more or what ????

2. ## Re: Trig Identity question

Originally Posted by sakonpure6

I solved this and I got -n for both a) and b) . Am I just tired and can't do math any more or what ????
$\cos(\pi+x)=\cos(\pi)\cos(x)-\sin(\pi)\sin(x)=-\cos(x)=-n$

$\sin(\frac{3\pi}{2}+x)=\sin(\frac{3\pi}{2})\cos(x) +\cos(\frac{3\pi}{2})\sin(x)=-\cos(x)=-n$

looks like you got both right to me.