# Find an angle between 0 and 2π that is coterminal with −9π/2? .

The arc (angle) $\frac{- 9 \pi}{2}$ has the same terminal as the arc
$\left(- \frac{\pi}{2} - \frac{8 \pi}{2}\right) = - \frac{\pi}{2}$
The arc $\left(- \frac{\pi}{2}\right)$ is co-terminal to the arc $\frac{3 \pi}{2}$