// S.Ayrinhac (2012)
// Centre et 
rayon du cercle circonscrit à un triangle quelconque

function [xc,yc,r]=Func_cercle_circonscrit_triangle(x,y)

x1=x(1);x2=x(2);x3=x(3);
y1=y(1);y2=y(2);y3=y(3);
a=x2-x1;
b=y2-y1;
c=x3-x2;
d=y3-y2;
x12=(x1+x2)./2;
y12=(y1+y2)./2;
x23=(x2+x3)./2;
y23=(y2+y3)./2;


xc=(y23-y12+c*x23/d-a*x12/b)/(c/d-a/b);
yc=y23-(xc-x23)*c/d;
r2=(x1-xc)*(x1-xc)+(y1-yc)*(y1-yc);
r=sqrt(r2);

endfunction