Q25 of 25 Page 9

The angle of elevation of the top of a tower standing on a horizontal plane from a point C is α. After walking a distance d towards the foot of the tower the angle of elevation is found to be β. The find the height of the tower.

To find: The height of the tower.


Explanation:



Let h be the height of the tower on horizontal plane.


Let α be the angle of elevation from point C and β be the angle of elevation from point B


Given CB = d


In Δ PCB




In Δ CDB





⇒ tanβ ( h - d tanα) = h tanα


⇒ h tanβ - d tan a tanβ = h tan a


⇒ h (tanβ – tan a) = d tan a tanβ



Use the formula:





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