To evaluate the expression for the inverse sine of negative one, we need to determine the angle whose sine value equals negative one. The inverse sine function, denoted as sin-1(x), is defined for angles between -\frac{\pi}{2} and \frac{\pi}{2}. This range corresponds to the first and fourth quadrants of the unit circle.

In the first quadrant (from 0 to \frac{\pi}{2}), all sine values are positive. Conversely, in the fourth quadrant (from -\frac{\pi}{2} to 0), sine values are negative. Since we are looking for the inverse sine of a negative value, our solution must lie in the fourth quadrant.

Specifically, we need to find the angle where the sine equals negative one. This occurs at -\frac{\pi}{2}, where the sine function reaches its minimum value. Therefore, the solution to the expression sin-1(-1) is:

-\frac{\pi}{2}

This result indicates that the angle corresponding to the sine of negative one is -90 degrees or -\frac{\pi}{2} radians.