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NDA Math Heights and Distance
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© examsnet.com
Question : 9
Total: 27
A ladder
6
m
long reaches a point
6
m
below the top of a vertical flagstaff. From the foot of the ladder, the elevation of the top of the flagstaff is
75
∘
. What is the height of the Flagstaff?
[NDA-I 2021]
11
m
9
m
(
6
+
√
3
)
m
(
6
+
3
√
3
)
m
Validate
Solution:
👈: Video Solution
Concept:
sin
θ
=
Perpendicular
Hypotenuse
sin
(
A
+
B
)
=
sin
A
⋅
cos
B
+
cos
A
⋅
sin
B
Calculation:
Length of the ladder
C
D
=
5
m
Length of staff from top to foot of the ladder
A
D
=
6
m
In
△
B
C
D
Using Trigonometric Ratio
sin
75
∘
=
B
D
C
D
sin
(
45
∘
+
30
∘
)
=
B
D
5
sin
45
∘
⋅
cos
30
∘
+
cos
45
∘
⋅
sin
30
∘
=
B
D
5
1
√
2
⋅
√
3
2
+
1
√
2
⋅
1
2
=
B
D
5
1
+
√
3
2
√
2
=
B
D
5
B
D
=
5
(
1
+
√
3
2
√
2
)
A
B
=
A
D
+
B
D
=
6
+
5
(
1
+
√
3
2
√
2
)
=
11
c
m
© examsnet.com
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