From an aeroplane vertically above a straight horizontal road


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From an aeroplane vertically above a straight horizontal plane, the angle of depression of two consecutive kilo-meter stones on the opposite sides of the aeroplane are found to be α and β. Show that the height of the aeroplanes is

Answered by admin @



So from fig 

we get tan α = h/x ⇒ x = h/tan α   ......   (i)

and tan β = h/(1-x)

⇒ 1 - h/tanβ = x  ............. (ii)

using i and ii we get

 ⇒ h/tan α = 1 - h/tanβ

⇒  h{(tan α + tanβ)/tanαtanβ} = 1

⇒ h = { \frac{tan \alpha tan \beta }{(tan \alpha + tan \beta )}

 PROVED

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