Answer:
y = -4/5
Step-by-step explanation:
Both coordinates are negative in the 3rd quadrant. The value of y is the other leg of the right triangle with hypotenuse 1. The Pythagorean theorem is helpful.
y = -√(1 -(-3/5)^2) = -√(1 -9/25) = -√(16/25)
y = -4/5
