Answer
-1
Work Step by Step
We have to determine $\sin\left(-\dfrac{\pi}{2}\right)$.
In the unit circle, we have:
$\sin\left(-\dfrac{\pi}{2}\right)=\dfrac{-perpendicular}{hypotenuse}=\dfrac{-hypotenuse}{hypotenuse}=-1$ (because $perpendicular=-hypotenuse$ for $-\dfrac{\pi}{2}$)
