Question

Not sure how to solve 2sinxcosx+cosx=0  Could you help?

Answer 1

$2sinxcosx+cosx=0\\\\cosx(2sinx+1)=0\iff cosx=0\ \vee\ 2sinx+1=0\\\\cosx=0\ \vee\ 2sinx=-1\ /:2\\\\cosx=0\ \vee\ sinx=-\frac{1}{2}\\\\x=\frac{\pi}{2}+k\pi\ \vee\ x=-\frac{\pi}{6}+2k\pi\ \vee\ x=\frac{7\pi}{6}+2k\pi\ to\ k\in\mathbb{Z}$