Point circle_center(Point pt[3]) { double x1,x2,x3,y1,y2,y3; double x = 0; double y = 0; x1 = pt[0].x; x2 = pt[1].x; x3 = pt[2].x; y1 = pt[0].y; y2 = pt[1].y; y3 = pt[2].y; x=((y2-y1)*(y3*y3-y1*y1+x3*x3-x1*x1)-(y3-y1)*(y2*y2-y1*y1+x2*x2-x1*x1))/(2*(x3-x1)*(y2-y1)-2*((x2-x1)*(y3-y1))); y=((x2-x1)*(x3*x3-x1*x1+y3*y3-y1*y1)-(x3-x1)*(x2*x2-x1*x1+y2*y2-y1*y1))/(2*(y3-y1)*(x2-x1)-2*((y2-y1)*(x3-x1))); Point center; center.x = x ; center.y = y ; return center; }