7. 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.
Suppose BC = is the height of transmission tower and the AB be the heoght of the building and AD is the distance between bulding and the observer point (D).
AB = 20 m, BC = m and AD = m