Q. 204.6( 8 Votes )

From a point P on the ground the angle of elevation of a 10 m tall building is 30°. A flag is hoisted at the top of the building and the angle of elevation of the top of the flag-staff from P is 45°. Find the length of the flag-staff and the distance of the building from the point P. (Take ).

Answer :

Let the height of the flag-staff = h (m)


And the distance of point P from foot of building = (m)


In ∆APB,


tan 45° =


tan 45° =


1 = =


h+10 = -------(1)


In ∆DPB,


tan 30° =


=


17.32 m. -----------(2)


On substituting value of in eqn. (1)



h =


h = 17.32-10 7.32 m.


Therefore height of flag-staff is 7.32 m. and distance of point P from tower is 17.32 m.


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