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JEE Main Math Class 11 Trigonometric Functions Questions
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© examsnet.com
Question : 41
Total: 115
The value of
cos
(
2
π
7
)
+
cos
(
4
π
7
)
+
cos
(
6
π
7
)
is equal to:
[27-Jun-2022-Shift-1]
−
1
−
1
2
−
1
3
−
1
4
Validate
Solution:
cos
2
π
7
+
cos
4
π
7
+
cos
6
π
7
=
sin
3
(
π
7
)
sin
π
7
cos
(
2
π
7
+
6
π
7
)
2
=
sin
(
3
π
7
)
⋅
cos
(
4
π
7
)
sin
(
π
7
)
=
2
sin
4
π
7
cos
4
π
7
2
sin
π
7
=
sin
(
3
π
7
)
2
sin
π
7
=
−
sin
π
7
2
sin
π
7
=
−
1
2
© examsnet.com
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