Equation of a Circle

Equation of a Circle in Standard Form

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    x2 + y2 = r2

The center of this circle is (0,0).  The radius of the circle is r. (r is greater than zero)

The extreme points of this circle are (-r, 0), (r ,0), (0, r), and (0, -r)

 

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(x - h)2 + (y - k)2 = r2

The center of this circle is ( h, k ).  The radius of this circle is r.

The extreme points of this circle are ( h - r, k ), ( h + r, k ), ( h, k + r ), and ( h, k - r )