Question

How do you evaluate `arccos(-1/2)`?

Answer 1

`theta`= 120, 240 degrees

Explanation:

Let `arccos(-1/2) =theta, then cos theta= -1/2`

It is known that cos 60 = `1/2`

Since `cos theta` is negative in IInd and IVth quadrant, `theta` would be = 180-60 and 180+60, that is 120,240 degrees.