from a point A i observe that the angle of elevation of the top of the tree is 21 degree i walk 10m toward the foot of the tree to obtain B from where the angle of elevation of the top of the tree is 34 degree,calculate the height of the tree above the level of the observation

Answer 1

500

Answer 2

the height is 50km

Answer 3

50 km? That's some tall tree. Did you draw a diagram? If so, it should be clear that the height h is found using
h cot21° - h cot34° = 10
h = 10/(cot21° - cot34°) = 8.9 m