Phicar's world

Hi, i was working in some geometric shit with circles, and one point was like "deduce the equation of the circle with 3 points" so i had a 3x3 type of equation, was to late and i am not in my wave in math so i decide to code it ...

there is the kramer law for a 3x3 equation

first a little explanation if we have a system like this Ax=B we can obtain x doing this x = (B/A) and we have a matrix with the constants of the equation so is basically x_n = Det[x_n]/Det[General]

where Det is the substracion of the addition of the multiplication of the cross values in matrix

here is the code enjoy it...

import java.io.*;
import java.util.*;
public class deter{
public static double coe[][]=new double[3][3];
public static double sol[] = new double[3];
public static void main(String args[]) throws IOException{
if(args.length<1){
System.err.println("Ingresa el archivo");
return;
}
BufferedReader lector = new BufferedReader(new FileReader(args[0]));
String tmp = "";
int p = 0;
while((tmp=lector.readLine())!=null){
if(p == 3){
StringTokenizer sr = new StringTokenizer(tmp,",");
for(int n = 0;n<3;n++)
sol[n]=Double.parseDouble(sr.nextToken());
break;
}
StringTokenizer st = new StringTokenizer(tmp);
for(int n = 0;n<3;n++)
coe[p][n]=Double.parseDouble(st.nextToken());
p++;
}
resolv();
}
public static void resolv(){
double d = Det(coe);
for(int n = 0;n<3;n++){
double tmp[][] = new double[3][3];
for(int w = 0;w<3;w++){
for(int e = 0;e<3;e++)
tmp[w][e]=coe[w][e];
}
for(int x = 0;x<3;x++)
tmp[x][n]=sol[x];
System.out.println(Det(tmp)/d);
}
}
public static double Det(double a[][]){
double c = 0,b = 0;
for(int n = 0;n<3;n++){
c+=(a[n][0]*a[(n+1)%3][1]*a[(n+2)%3][2]);
b+=(a[(n+0)%3][2]*a[(n+1)%3][1]*a[(n+2)%3][0]);
}
return c-b;
}
}

Pd: the file need to be in this way

x₁ y₁ z₁
x₂ y₂ z₂
x₃y₃ z₃
res₁,res₂,res₃