Question

How do I find the value of cos 5pi / 6?

Answer 1

Find exact value of `cos ((5pi)/6)`

Ans: `sqrt3/2`

Explanation:

On the trig unit circle,
`cos ((5pi)/6) = cos (- pi/6 + pi) = - cos (pi/6)`
Trig Table of Special Arcs gives -->
`cos ((5pi)/6) = - cos (pi/6) = - sqrt3/2`