Answer:
y = [tex]\sqrt{r^{2}- x^{2} }[/tex]
Work Shown:
Use the Pythagorean theorem to solve for y
a^2 + b^2 = c^2
x^2 + y^2 = r^2
y^2 = r^2 - x^2
y = sqrt(r^2 - x^2)