Program/Source code for calculating the radius of the circle with three corodinate points using C#.net

using System;

namespace center_radius__circle_given_only_three_points
{
class Program
{
static void Main(string[] args)
{
double x1=0, x2=0, x3=0, y1=0, y2=0, y3=0;

Console.WriteLine("Finding RADIUS & CENTRE of the circle that goes through the given three points");

Points[] points = new Points[3];

for (int i = 0; i <= 2; ++i)
{
points[i] = new Points();
Console.Write("\nx{0} = ", i+1);
double x = Convert.ToDouble(Console.ReadLine());
points[i].setX(x);

Console.Write("y{0} = ", i+1);
double y = Convert.ToDouble(Console.ReadLine());
points[i].setY(y);
}

Console.WriteLine();

for (int i = 0; i <= 2; ++i)
{
x1 = points[0].getX();
y1 = points[0].getY();

x2 = points[1].getX();
y2 = points[1].getY();

x3 = points[2].getX();
y3 = points[2].getY();
}

double mr = (double)((y2 - y1) / (x2 - x1));
double mt = (double)((y3 - y2) / (x3 - x2));

double xc = (double)((mr*mt*(y3 - y1) + mr*(x2 + x3) - mt*(x1 + x2)) / (2*(mr - mt)));

double yc = (double) ((-1 / mr)* (xc - (x1 + x2)/2) + (y1 + y2)/2);

Console.WriteLine("Center Points xc = {0} yc = {1}", xc, yc);

double d = (xc - x1) * (xc - x1) + (yc - y1) * (yc - y1);

double r = Math.Sqrt(d);

Console.WriteLine("\nRadius = {0}", r);

Console.ReadKey();
}
}
}
class Points
{
double x;
double y;

public double getX()
{
return this.x;
}
public void setX(double x)
{
this.x = x;
}

public double getY()
{
return this.y;
}
public void setY(double y)
{
this.y = y;
}
}

Here you go. The attached file is a zipped up VS 2010 Windows Forms app which lets you input the coordinates of the 3 point and calculates the coordinate of the center of the circle and it radius. I wrote it really fast so if you find a bug it'll be good exercise for you to fix it. :) I got the formulas from this site:

http://regentsprep.org/Regents/math/geometry/GCG6/RCir.htm

hi

hi,

In ur formula, but we can not find radus,
can u please about requirment why u required this?

Hi  Karthi,
i m sure that this link will help you-
http://paulbourke.net/geometry/circlefrom3/