摘要
A circle is the set of all points in a planeequidistant from a fixed point called the centerpoint.We can derive theequation directly from thedistance formula.If weplace the center point onthe origin point,theequation of a circle
A circle is the set of all points in a plane equidistant from a fixed point called the center point. We can derive the equation directly from the distance formula. If we place the center point on the origin point, the equation of a circle with center point （0, 0） and radius r is x^2 ＋ y^2 =r^2。
