radius of a circle

Question

for a finding of radius of circle whats the formulae?

Answer 1

Formulae for finding radius of circle

If we know the diameter of circle, we can use the formula for r = D/2.

If we know the circumference of cicle,  we can use the formula for r = C/2*pi

If we know the area of circle, we can use the formula for r = √(A/pi)

If we know the circle equation form x^2+y^2+2gx+2fy+c = 0,we use the formula for r = √(g^2+f^2-c)