Question

How do you calculate the `cos^-1 (-1/2)`?

Answer 1

`cos^(-1)(-1/2)= (2pi)/3`

Explanation:

If `cos^(-1)(-1/2) = theta`
then
`color(white)("XXX")cos(theta)=-1/2`
with a further restriction `0 <= cos^(-1) <= pi`

From the above diagram, we can see
`color(white)("XXX")theta=(2pi)/3`