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RRB Junior Engineer Stage 1 Model Papers 10
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© examsnet.com
Question : 4
Total: 98
The angles of elevation of the top of a tower standing on a horizontal plane from two points on a line passing through the foot of the tower at a distance 9 ft and 16 ft respectively are complementary angles. Then the height of the tower is
9 ft
12 ft
16 ft
144 ft
Validate
Solution:
In ∆ABC
tan
α
=
h
9
....(1)
In ∆ABD
tan
β
=
h
16
α
+
β
=
90
°
(given)
β
=
90
−
α
Since
tan
β
=
h
16
tan
(
90
−
α
)
=
h
16
⇒
cot
α
=
h
16
or
tan
α
=
16
h
....(2)
From eqn.(1) and (2)
h
9
=
16
h
⇒
h
2
=
16
×
9
⇒
h
=
12
f
e
e
t
© examsnet.com
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