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WBJEE 2016 Math Solved Paper
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© examsnet.com
Question : 43
Total: 75
1 +
n
C
1
cos θ +
n
C
2
cos 2θ + ..... +
n
C
n
cos nθ equals
(
2
c
o
s
θ
2
)
n
c
o
s
n
θ
2
2
c
o
s
2
n
θ
2
2
c
o
s
2
θ
2
(
2
c
o
s
θ
2
)
n
Validate
Solution:
Re (
n
C
0
+
n
C
1
e
i
θ
+ .....) = Re
(
1
+
e
i
θ
)
2
= Re
(
c
o
s
θ
+
1
+
i
s
i
n
θ
)
n
=
(
2
c
o
s
(
θ
2
)
)
2
c
o
s
(
n
θ
2
)
© examsnet.com
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