Solution:
Let BC be the 20 meter high building.
The elevation is taken from D, which is a point on the ground.
Transmission tower’s height = AC – BC = AB
We need to find: The height of the tower i.e. AB,
From figure, In right angle ΔBCD,
BC/CD = tan 45°
1 = 20/CD
CD = 20
Again,
In right ΔACD,
AC/CD = tan 60°
AC/20= √3
AC = 20√3
Now, AC – BC = AB = (20√3-20) = 20(√3-1)
As a result, transmission tower’s height is 20(√3 – 1) m.