Tardigrade
Tardigrade - CET NEET JEE Exam App
Exams
Login
Signup
Tardigrade
Question
Mathematics
The value of the expression cos 4 (π/8)+ cos 4 (3 π/8)+ cos 4 (5 π/8)+ cos 4 (7 π/8)=
Q. The value of the expression
cos
4
8
π
+
cos
4
8
3
π
+
cos
4
8
5
π
+
cos
4
8
7
π
=
1832
221
Report Error
A
1
12%
B
2
25%
C
2
3
62%
D
4
0%
Solution:
cos
4
8
π
+
cos
4
8
3
π
+
cos
4
8
5
π
+
cos
4
8
7
π
=
2
(
cos
4
8
π
+
sin
4
8
π
)
=
2
[
(
cos
2
8
π
+
sin
2
8
π
)
2
−
2
cos
2
8
π
sin
2
8
π
]
=
2
(
1
−
4
1
)
=
2
3