One of the basic and exam oriented question from trigonometry as it was already asked in previous year paper of 2011 in which we have to find the height of the tower when the angle of elevation of the top of a vertical tower from a point on the ground is 60° . From another point 10 m vertically above the first, its angle of elevation is 45°.
Book RS Aggarwal, Class 10, chapter 14, question no 21
Hope it helps you.