Question 372540
If you have a point on the circle and you have the center of the circle, then the distance from the point to the center is equal to the radius of the circle.
Use the distance formula,
{{{R^2=(x[2]-x[1])^2+(y[2]-y[1])^2}}}
Any of the points and the center will work.
I'll use ({{{1}}},{{{3}}}) and the center ({{{-6}}},{{{3}}})
{{{R^2=(1-(-6))^2+(3-3)^2}}}
{{{R^2=(7)^2+(0)^2}}}
{{{highlight(R=7)}}}
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{{{drawing(300,300,-14,2,-4,12,grid(1),
circle(1,3,0.3),
circle(-6,3,0.3),
circle(-13,3,0.3),
circle(-6,10,0.3),
graph(300,300,-14,2,-4,12,0))}}}