The angles of elevation of the top of a lamppost as seen from a point 40 m away from the post's foot are 30^o. Find the height of the lamp post.

According to the question:

Let the height of the lamp post be h meter.

From the figure, $\tan 30°=\frac{\mathrm{h}}{40}$

$\frac{1}{\sqrt{3}}=\frac{\mathrm{h}}{40}$

$\mathrm{h}=\frac{40}{\sqrt{3}}$

$\mathrm{h}=\frac{40\sqrt{3}}{3} \mathrm{m}$

Thus, the height of the lamp post is 30 m.