### Instruction: Find $\sin \left( -\frac{\pi}{2} \right).$.### Response: I know that $\sin \left( -\frac{\pi}{2} \right)$ is the same as $-\sin \left( \frac{\pi}{2} \right)$ by the oddness property of sine.
I also know that $\sin \left( \frac{\pi}{2} \right)$ is 1 by the unit circle definition of sine.
Therefore, $\sin \left( -\frac{\pi}{2} \right)$ is $-1$.