The angle of elevation of the top of a chimney from the top of a tower is `60^@` and t he angle of depression of the foot of the chimney from the top of the tower is `30^@` . If the height of the tower is 40 m, find the height of the chimney. According to pollution control norms, the minimum height of a smoke emitting chimney should be 100 m. State if the height of the above mentioned chimney meets the pollution norms. What value is discussed in this question?