The value of- ( 2 cos left ( π 13 right ) cos left ( 9 π 13 right ) + cos left ( 3 π 13 right ) + cos left ( 5 π 13 right ) ) is-

2 \cos{\left ( \frac{π}{13} \right )} \cos{\left ( \frac{9 π}{13} \right )} + \cos{\left ( \frac{3 π}{13} \right )} + \cos{\left ( \frac{5 π}{13} \right )}

IUT 11-12

2 \cos{\left ( \frac{π}{13} \right )} \cos{\left ( \frac{9 π}{13} \right )} + \cos{\left ( \frac{3 π}{13} \right )} + \cos{\left ( \frac{5 π}{13} \right )}

IUT 11-12