Question

How do you evaluate `cos^-1(sin(-pi/6))` without a calculator?

Answer 1

`+- (2pi)/3`

Explanation:

Use trig table and unit circle -->
`sin (- pi/6) = - 1/2`
`cos ^-1 (-1/2) = arccos x = arccos (-1/2)` -->
`x = +- (2pi)/3`