How Many Conditions Are Needed to Specify a Circle?

[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 ??

 

[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.

See this thread:

https://www.physicsforums.com/showthread.php?t=24014