Ask the algorithm of triangular external round coordinate

///

/ / Seek triangular external round coordinates

///

Void circle_center (Point * Center, Point Pt [3], Double * Radiu)

{

Double X1, X2, X3, Y1, Y2, Y3;

Double x = 0;

Double y = 0;

X1 = pt [0] .pt.x;

X2 = Pt [1] .pt.x;

X3 = pt [2] .pt.x;

Y1 = pt [0] .pt.y;

Y2 = pt [1] .pt.y;

Y3 = pt [2] .pt.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)));

Center-> pt.x = x;

Center-> pt.y = y;

* RADIU = (Pt [0] .pt.x - x) * (Pt [0] .pt.x - x) (Pt [0] .pt.y - y) * (PT [0] .pt. Y - Y);

}