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The value of sum(r=1)^(18) cos^(2)(5r)^(...

The value of `sum_(r=1)^(18) cos^(2)(5r)^(@)`, where `x^(@)` denotes the x degree, is equal to

A

0

B

`7/2`

C

`(17)/(2)`

D

`(25)/(2)`

Text Solution

Verified by Experts

The correct Answer is:
C
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