The sine function has a period of 360 degrees, which means that adding or subtracting any multiple of 360 degrees to the angle argument of the sine function does not change its value. So, we can simplify the argument of sin(-690) by adding a multiple of 360 degrees to bring it within the range of one period of the sine function:

sin(-690) = sin(-690 + 2 360) = sin(30)

The value of sin(30) is 1/2.

So, the value of sin(-690) is 1/2.