Trigonometry 7th Edition

$\theta=90^{\circ}or \,270^{\circ}$
$\sin\theta\cos\theta-2\cos\theta=0$ $\cos \theta(\sin\theta-2)=0$ So, either $\cos\theta=0\,or\,\sin\theta=2$ When, $\cos\theta=0,$ $\theta=90^{\circ},270^{\circ}$ Now, $\sin\theta=2$ is not possible, since $|\sin\theta|\leq1$ For, $0^{\circ}\leq\,x\lt360^{\circ}$ So, $\theta=90^{\circ}or \,270^{\circ}$