Find the reference angles corresponding to each of the following angles. It may help if you sketch `theta` in standard position. `theta=640^@`

Explanation

(i) `theta=-230^@`

Hence, the reference angle is `50^@`.
(ii) `theta=(31pi)/9`
`theta=(31pi)/9=3pi+(4pi)/9`

Hence, the reference angle is `(4pi)/9`.
(iii) `theta=640^@`

here, `theta=2xx360^@-80^@`
Hence, the reference angle is `80^@`.