Question

Evaluate cos11pi /6
-square root of 3/2
-1/2
1/2
square root of 3/2

Answer 1

$\displaystyle cos \frac{11 \pi}{6}= cos (\frac{3 \pi}{2} + \frac{ \pi}{3})=sin \frac{ \pi}{3}= sin 60^{\circ}=\frac{ \sqrt3}{2}$

Answer is 4) square root of 3 / 2