Question

Find the reference angles corresponding to given angles. It may help if you sketch $\theta$ in standard position, $\frac{31\pi }{9}$ is $\frac{a\pi }{9}$ Find a.

Answer 1

$\theta =\frac{31\pi }{9}$

$\theta =\frac{31\pi }{9}=3\pi +\frac{4\pi }{9}$

Hence, the reference angle is $\frac{4\pi }{9}$.
$\therefore a=4$