Question

How do you evaluate `cos ((5pi)/6)`?

Answer 1

`-sqrt3/2`

Explanation:

Trig unit circle, trig table, and property of supplement arcs -->
`cos ((5pi)/6) = cos (-pi/6 + (6pi)/6) = cos (-pi/6 + pi) =`
`= - cos (-pi/6) = - cos (pi/6) = - sqrt3/2`