# The angle of elevation of the tower from certain point is 300. If the observer moves 20 m towards the tower, the angle of elevation of the top increase by 150.Find the height of the tower.

Let PR = h meter, be the height of the tower.

The observer is standing at point Q such that, the distance between the observer and tower is QR = (20+x) m, where

QR = QS + SR = 20 + x

PQR = 30°

PSR = θ In ∆PQR,  Rearranging the terms,

We get 20 +x = √3 h In ∆PSR, Since, angle of elevation increases by 15 when the observer moves 20 m towards the tower. We have,

θ = 30° + 15° = 45°

So,  h = x

Substituting x=h in eq. 1, we get

h = √3 h – 20

3 h h = 20

h (3 - 1) = 20 Rationalizing the denominator, we have    = 10 (√3 + 1)

Hence, the required height of the tower is 10 (√3 + 1) meter.

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