Find Equation of a Circle - applet

An html 5 applet generates the graph of a circle. The equations of the circle is of the form:
(x - h)2 + (y - k)2 = r2

where (h , k) is the center of the circle and r its radius.
As an exercise, you need to find an equation to the circle generated. And you can check your answer.

Interactive Tutorial

1 - click on the button "New Circle" to generate a new circle whose center is also plotted.
2 - From the graph, determine h and k which are the x and y coordinates of the center of the circle respectively. Then find a point on the graph of the circle and use it to find the radius r. Then write the equation as follows:
(x - h)2 + (y - k)2 = r2

More References and links

tutorial on circles
Match Equations of Circles to Graphs. Excellent interactive activity where equations of circles are matched to graphs.
Three Points Circle Calculator.

Computer Technology Simply Explained