Mathematics : PU-CET (U.G) 2015 Panjab University Entrance Exam With Answers

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7.

Given that $\displaystyle\sum_{k=0}^{n-1} cos \frac{2k\pi}{n}$ = 0 , the value of $\displaystyle\sum_{k=1}^{n-1} cos^2 \frac{k\pi}{n}$ is :

A: 0
B: 1
C: $\frac{1}{2}$(n-2)
D: $\frac{1}{2}$(n-1)

The answer is: C

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