An important and exam oriented question from trigonometry as it was already asked in previous year paper of 2014 in which we are to calculate the height of the chimney when the angle of elevation of the top of a chimney from the foot of a tower is 60 degree. And the angle of depression of the foot of the chimney from the top of the tower is 30 degree. If the height of tower is 40 m.
Book RS Aggarwal, Class 10, chapter 14, question no 18
Hope it helps you