B. A flag-staff stands on the top of a 5 m high tower. From a point on the ground, the angles
elevation of the top of the flag-staff is 60° and from the same point, the angle of elevation of the
top of the tower is 45°. Find the height of the flag-staff.
[CBSE 2013
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Answer:
the height of the flagstaff is 3.66 m.
Step-by-step explanation:
Let BC be the height of the tower and DC be the height of the flag-staff.
In right angle triangle ABC,
AB=BC cos 45°
AB=5m........(1)
In right angle triangle ABD,
AB=BD cot 60°
AB= (BC+CD) cot 60°
AB=(5+CD) 1/√3..........(2)
equating 1&2
(5+CD)1/√3=5
CD=5√3-5
=5× 0.732
=3.66m
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