\[\boxed{\mathbf{624}\mathbf{.}}\]
\[1)\ \sqrt{3}\cos x + \sin x = 0\ \ \ |\ :\cos x\]
\[\sqrt{3} + tg\ x = 0\]
\[tg\ x = - \sqrt{3}\]
\[x = - arctg\ \sqrt{3} + \pi n\]
\[x = - \frac{\pi}{3} + \pi n.\]
\[Ответ:\ - \frac{\pi}{3} + \pi n.\]
\[2)\cos x = \sin x\ \ \ \ \ |\ :\cos x\ \]
\[1 = tg\ x\]
\[x = arctg\ 1 + \pi n\]
\[x = \frac{\pi}{4} + \pi n.\]
\[Ответ:\ \ \frac{\pi}{4} + \pi n.\]
\[3)\sin x = 2\cos x\ \ \ \ \ |\ :\cos x\]
\[tg\ x = 2\]
\[x = arctg\ 2 + \pi n.\]
\[Ответ:\ \ arctg\ 2 + \pi n.\]
\[4)\ 2\sin x + \cos x = 0\ \ \ \ \ |\ :\cos x\]
\[2\ tg\ x + 1 = 0\]
\[2\ tg\ x = - 1\]
\[tg\ x = - \frac{1}{2}\]
\[x = - arctg\frac{1}{2} + \pi n.\]
\[Ответ:\ - arctg\frac{1}{2} + \pi n.\]