Final answer:
The exact value of sin(-210 degrees) with the aid of its reference angle is -√3/2.
Step-by-step explanation:
To find the exact value of sin(-210 degrees) using the reference angle, we need to find the equivalent angle in the first quadrant. Since sin is negative in the third quadrant, we can use the reference angle of 210 degrees in the first quadrant.
The reference angle is the angle formed between the x-axis and the terminal side of the angle, and it has the same sine value as the original angle.
In the first quadrant, the sine of 210 degrees is -√3/2.