# Trig Identity question

• January 27th 2014, 05:20 PM
sakonpure6
Trig Identity question
Attachment 30095
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 ????
• January 27th 2014, 05:32 PM
romsek
Re: Trig Identity question
Quote:

Originally Posted by sakonpure6
Attachment 30095
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.