Question
From a point on the ground, the angles of elevation of the bottom and the top of a transmission tower fixed at the top of a 20 m high building are 45° and 60° respectively. Find the height of the tower.
Solution
Let CD be the transmission tower of height h m. fixed on a building of height 20 m.
i.e., CD = h m
and BC = 20 m.
The angles of elevation of the bottom C and top D of the transmission tower are 45° and 60° respectively.
i.e., ∠BAC = 45°
and ∠BAD = 60°
In right triangle ABC, we have
In right triangle ABD, we have
Comparing (i) and (ii) we get
Hence, height of the transmission tower is 
