Answer
no solution
Work Step by Step
$\sin^2\theta=4-2\cos^2\theta$
$\sin^2\theta+2\cos^2\theta=4$
$\sin^2\theta+\cos^2\theta+\cos^2\theta=4$
$1+\cos^2\theta=4$
$\cos^2\theta=3$
$\cos \theta=\pm\sqrt{3}$
Since cosine can be only between -1 and 1, and $\pm\sqrt{3}$ is outside this range, there is no solution.
