Evaluate: Trigonometry Relation #02

Evaluate:

The angles of depression of the top and bottom of a building 50 metres high
Prove that Trigonometry Relation #04
Evaluate: Trigonometry Relation #03
Two poles of equal heights are standing opposite to each other
Evaluate: Trigonometry Relation #01
As observed from the top of a 100 m high light house from the sea-level, the angles of depression of two ships
Amit, standing on a horizontal plane, finds a bird flying at a distance of 200 m
A, B, C are interior angles of ΔABC. Prove that cosec (A+B)/2 = sec C/2