The general form of the equation of a circle is given as
(x-a)^2 + (y - b)^2 = r^2
where a and b are points at the center of the circle and r is the radius of the circle.
Hence given that the center has points 2+, 0 and the points on the circle are 7+,2.2), the length of the radius can be computed by substituting these values into the general equation of a circle.
(7 - 2)^2 + (2.2 - 0)^2 = r^2
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