Circle conditions

1. Mar 16, 2010

phymatter

the general equation of a circle has 3 constants , so it is said that 3 conditions , like 3 points (on the circle) are required to specify a circle , but , we require only the center and radius to specify a circle , so how many conditions are actually required ??

2. Mar 16, 2010

hotvette

The center is two pieces of information, an x-coordinate and a y-coordinate, thus three total. If you have x-y coordinates of 3 points, you can write 3 equations with 3 unknowns and solve for the radius and the coordinates of the center.