Question

What does `arcsin(cos ((-2pi)/3))` equal?

Answer 1

`-pi`/6

Explanation:

cos (`-`2`pi`/3 ) = sin ( `pi`/2 + (`-2pi`/3`)) = sin (-`pi#/6)
arc sin (sin) is unit operator 1.

Answer 2

(7pi)/6 and (11pi)/6

Explanation:

On the trig unit circle,
`cos ((-2pi)/3) = = cos (2pi)/3 = - 1/2`
`sin x = -1/2` --> arc `x = - pi/6` and `x = -(5pi)/6.`
Answer using positive arcs (co-terminal arcs):
`x = (7pi)/6` and `x = (11pi)/6`