How do you label the angle of depression and angle of elevation? ?

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Answer 1

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Angles of Depression or elevation are measured with respect to the horizontal line 

passing through the point of observation.

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Refer to the following figure. Angle of 

Elevation is CAO = 47°  :   Depression is OAB = 36°

We have to calculate Height of the building CB = x m (say)

Hence OC = (x-120) m ,  OB  =  120 m

Tan (47°)  =  CO/AO = (x-120)/AO

=> (x-120)/AO  =  Tan 47°   

=> AO  =  (x-120)/Tan 47°   ..................(1)

From Triangle ABO :  BO/AO = Tan 36°

=> AO  =  1230/Tan36° .............. (2)

From (1) and (2) ---

(x-120)/Tan 47°  =   120/Tan36°

=>  ( x - 120 )  =  120 * [ Tan 47/Tan 36 ] = 177.1187

=>  x  =  297.1187 m  ............ Answer