Answer
$-90°$
Work Step by Step
To convert from radians to degrees, the measurement in radians must be multiplied by $\frac{180°}{\pi}$.
Therefore
$-\frac{\pi}{2} \text{ radians}= -\frac{\pi}{2} \times \frac{180°}{\pi}$
$=-\frac{180°}{2}$
$=-90°$
