A boy standing on a horizontal plane finds a bird flying at a distance of 100m from him at an elevation of 30°. A girl standing on the roof of 20-meter high building finds the angle of elevation of the same bird to be 45°. Both the boy and the girl are on opposite sides of the bird. Find the distance of the bird from the girl.

An aeroplane at an altitude of 200 m observes the angle of depression of opposite points on the banks of a river to be 45° and 60°. Find in metres the width of the river.

An aircraft is flying at a constant height with a speed of 360 km/hr. From a point on the ground, the angle of elevation at an instant was observed to be 45°. After 20 sec. the angle of elevation was observed to be 30°. Determine the height at which the aircraft is flying (√3 + 1) km or 2.732 km.

Two trees A and B are on the same side of a river. From a point C in the river, the distance of the trees A and B is 250 m and 300 m respectively. If the angle C is 45o find the distance b/w the trees (use root 2 = 1.44).

At the foot of the mountain, the elevation of its summit is 45°, after ascending 1000m towards the mountain up a slope of 30°, inclination the elevation found to be 60°. Find the height of the mountain.