COULD y=sqrt (1-x^2) in GRAPH calculate pi (3.14159...)???

Question

Its radius in a circle equals one, so a one-quarter circle equals just over 1.57 times its radius. Then 1.57 multiplied by 4 (as one-quarter circle multiplied by 4 to make a full circle) equals DOUBLE pi (6.28318...). So to equal SINGLE pi, its radius equals 1/2, so a one-quarter circle equals just over 0.78 its radius. Then 0.78 multiplied by 4 (as one-quarter circle multiplied by 4 to make a full circle) equals SINGLE pi.

Answer 1

Any circle can be used to calculate pi.
pi = circumference / (2* r)