Question

Find the exact value by using a half-angle identity.
cos{5pi/12}

Answer 1

half-angle identity
\[\cos(\theta/2) = \pm \sqrt{\frac{1+\cos \theta}{2}}\]
theta = 5pi/6

Answer 2

find cos(5pi/6)

Answer 3

-\[-\sqrt{3}/2\]

Answer 4

yep, now plug that in and simplify