JEE MATHEMATICS MCQ: TRIGONOMETRY RATIOS

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Application +4 | -1

If a

=\pi / 18

rad, then

\cos a+\cos 2 a+\ldots .+\cos 18 a

is equal to

View answer and explanation

Correct option: A

Option A (0) is correct because the sum telescopes to 0 due to the symmetry around

\frac{\pi}{2}

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