解方程 $4\sin\theta+\tan\theta=0$，其中 $0^\circ<\theta<180^\circ$。

先把正切写成正弦除以余弦。题给开区间内正弦始终为正，因此可以约掉它。

The original equation requires $\cos\theta\ne0$. Multiplying through by $\cos\theta$ gives

Since $\sin\theta>0$ for $0^\circ<\theta<180^\circ$, we need $\cos\theta=-1/4$. The unique solution in this interval is $\theta=104.5^\circ$ to one decimal place.