look at your picture
notice the coordinates for the center of the circle, the x,y or h,k values
notice how long the radius is
thus [tex]\bf \qquad \textit{equation of a circle}
\\\\\\
(x-{{ h}})^2+(y-{{ k}})^2={{ r}}^2
\qquad center\ ({{ h}},{{ k}})\qquad
radius={{ r}}[/tex]
