Question

Two buildings are in front of each other on a road of width 15 meters. From the top of the first building, having a height of 12 meter, the angle of elevation of the top of the second building is 30°.What is the height of the second building?

Answer 1

Let AB and CD be the two building standing on the road.
Suppose the height of the second building be h m.

Here, AB = 12 m, BD = 15 m, ∠CAE = 30º and AE ⊥ CD. 
CE = CD − ED = (h − 12) m            (ED = AB)
AE = BD = 15 m
In right ∆AEC,
\[\tan30^\circ = \frac{CE}{AE}\]

\[ \Rightarrow \frac{1}{\sqrt{3}} = \frac{h - 12}{15}\]

\[ \Rightarrow h - 12 = \frac{15}{\sqrt{3}} = 5\sqrt{3}\]

\[ \Rightarrow h = \left( 12 + 5\sqrt{3} \right) m\]

Thus, the height of the second building is 

\[\left( 12 + 5\sqrt{3} \right)\] m.