circle with three points

Im writing a program that accepts three points (?, ?) on a circle in a 2- dimensional Cartesian plane as input and returns the center, radius, and vectors ABC from the general equation of a circle ?^2 + ?^2 + A? + B? + C = 0. I know that one can systems of linear equations to solve for ABC however, I don't know how to do it. I started with the program below:

x1 = input('\nEnter first X coordinate: ');
y1 = input('\nEnter first Y coordinate: ');
x2 = input('\nEnter second X coordinate: ');
y2 = input('\nEnter second Y coordinate: ');
x3 = input('\nEnter third X coordinate: ');
y3 = input('\nEnter third Y coordinate: ');

eq1 = x1D + y1E + F == -(x1*2)+(y1*2);
eq2 = x2D + y2E + F == -(x2*2)+(y2*2);
eq3 = x3D + y3E + F == -(x3*2)+(y3*2);

I'd appreciate any help and suggestion. Thank you very much :)

[Stephane]

An answer here (File Exchange entry) ?

Answer 1

[Jim Riggs]

Try this.

Answer 2

[Image Analyst]

The answer is in the FAQ: How_can_I_fit_a_circle_to_a_set_of_XY_data?