A T.V. tower stands vertically on a bank of a river. From a point on the other bank directly opposite the tower, the angle of elevation of the top of the tower is 60°. From a point 20 m away this point on the same bank, the angle of elevation of the top of the tower is 30°. Find the height of the tower and the width of the river.
Let BC be the height of the T.V tower and AB be the width of the river.
In ∆ABC,
tan 60° = 
√3 = 
------(1)
In ∆ABC,
tan 30° = 
tan 30° = 
= 
√3h = 20+
---------(2)
On substituting value of h in eqn.(2)
√3× √3
= 20+
3
3
2
On substituting value of 
in eqn. (1)
h = √3 
h = 10√3 m.
Therefore height of T.V tower is 10√3 m. and width of river is 10 m.
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