posted by akash .
from the top of a cliff 50 m high the angle of depression of the top and bottom of tower are observed to be 30 and 45 degree resp. find h of tower ?
well, you know the distance to the base of the tower is 50 m (a 45 deg angle).
Then, you can compute the length of the hypotenuse of that triangle on the common side (ie, 50sqrt2).
now you have one angle (15 deg, one side, and another angle (the 45 deg angle from the tower to the long side 50sqrt2)
Now use the law of sines: