Question

cos pi/13 + cos (5pi)/13 + cos (8pi)/13 + cos (12pi)/13 =​

Answer 1

Step-by-step explanation:

We have,

$\tt cos \bigg( \frac{\pi}{13} \bigg) +cos \bigg( \frac{5\pi}{13} \bigg) + cos \bigg( \frac{8\pi}{13} \bigg) + cos \bigg( \frac{12\pi}{13} \bigg)$

$\tt = cos \bigg( \frac{\pi}{13} \bigg) +cos \bigg( \frac{5\pi}{13} \bigg) + cos \bigg( \pi - \frac{5\pi}{13} \bigg) + cos \bigg( \pi - \frac{\pi}{13} \bigg)$

$\tt = cos \bigg( \frac{\pi}{13} \bigg) +cos \bigg( \frac{5\pi}{13} \bigg) - cos \bigg( \frac{5\pi}{13} \bigg) - cos \bigg( \frac{\pi}{13} \bigg)$

$= 0$

Answer 2

Answer:

Step-by-step explanation: