The length of the shadow of a vertical tower on level ground increased by 10 m when the altitude of the sum changes from 45° to 30°. The height of the tower is:

Answer: Option C

Solution

Answer: Option C

Solution:

$$\begin{array}{rl}& AB=10\\ & \left(\sqrt{3}-1\right)\to 10\\ & 1\to \frac{10}{\sqrt{3}-1}\\ & =\frac{10\left(\sqrt{3}+1\right)}{2}\\ & =5\left(\sqrt{3}+1\right)\end{array}$$