Q13 of 28 Page 93

From a point at a distance of 120 m from the base of an incomplete tower the angle of elevation of the top of the tower is 30°. Find how much more height the tower be made so that its angle of elevation at the same point becomes 60°?


Let total height is g, Incomplete Tower Height is DB.


Given Angle of Elevation of the top is 60o, Angle of Elevation of the Incomplete Tower is 30o. AB = 120.


in ABD,






(rationalization)



DB = 40√3


in BAC,





BC = 120√3


Increase in Height To change the angle of Elevation = 120√3 – 40√3 = 80√3


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