Question

What is the inverse cosine of 1/3?

Answer 1

`theta~~70.53^@, 289.47^@`

Explanation:

Since `1/3` is not a ratio we can find in a special triangle, we must use a calculator:

`costheta=1/3`
`theta=cos^-1(1/3)`
`theta~~70.53^@`

However, since cosine is also positive in quadrant `4` according to the CAST rule, there is a second answer:

`theta=360^@-70.53^@`
`theta~~289.47^@`