Question : A person from the top of a hill observes a vehicle moving towards him at a uniform speed. It takes 10 minutes for the angle of depression to change from $45^{\circ}$ to $60^{\circ}$. After this, the time required by the vehicle to reach the bottom of the hill is:

Question : A man standing on the bank of a river observes that the angle subtended by a tree on the opposite bank is 60°. When he retreats 36 m from the bank, he finds that the angle is 30°. The breadth of the river is:

Question : A boat is moving away from an observation tower. It makes an angle of depression of 60° with an observer's eye when at a distance of 50 metres from the tower. After 8 seconds, the angle of depression becomes 30º. By assuming that it is running in still water,

Question : From the top of a 20 metres high building, the angle of elevation from the top of a tower is 60° and the angle of depression of its foot is at 45°, then the height of the tower is: $(\sqrt{3} = 1.732)$

Question : A man standing on the bank of a river observes that the angle of elevation of the top of a tree just on the opposite bank is $60°$. But the angle of elevation is $30°$ from a point which is at a distance $20\sqrt{3}$ ft away from the bank. Then the