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Circle:  The set of all points in a plane equidistance from a given point


center:  (h,k) 




r^2= (x-h)^2 +  (y-k)^2




Standard Form: (x-h)^2 + (y-k)^2 = r^2


General Form: x^2 + y^2 + Dx + Ey + F = 0