[Topic: Height and Distances]
A tower stands at the centre of a circular park. If A and B are two points on the boundary of the park, such that AB = a m subtends an angle of 60° at the foot of the tower and the angle of elevation of the top of the tower from A or B is 30°. Find the height of the tower.
Answers
Answer:
a/√3
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Given :-
A tower stands at the centre of a circular park. If A and B are two points on the boundary of the park, such that AB = a m subtends an angle of 60° at the foot of the tower and the angle of elevation of the top of the tower from A or B is 30°.
To Find :-
Height of tower
Solution :-
Let height of tower = h
We know that radius of a circle is always equal.
AC = BC.
Then
∠ABC = ∠BAC
Since two sides are equal it must be an isosceles triangle.
Now,
In ΔABC
⇒ ∠ABC + ∠BAC + ∠CAB = 180
⇒ ∠ABC + ∠ABC + 60 = 180
⇒ 2∠ABC = 180 - 60
⇒ 2∠ABC = 120
⇒ ∠ABC = 120/2
⇒ ∠ABC = 60°
⇒ ∠ABC = ∠BAC = ∠BCA = 60°
It must be an equilateral triangle.
We know that sides of equilateral triangle are equal
AB = BC = BA
Let the side of equilateral triangle be x
Now
h = AC tan (30)° = BC tan (30)°
⇒ h = BC tan(30)°
⇒ h = x × 1/√3
⇒ h = x/√3
Hence,
The height of tower is x/√3 m