I'm trying to use IModelDoc2 :: CreatePlaneFixed2 and ISketchManager::CreateSpline

to create a Spline from a 3DSketch of 3 points.

The problem is that when I pass the coordintes of points after CreatePlaneFixed2 I can't pass the right

coordinate of the 3rd point. Can someone help me?

Part of my code in C#:

                    double a, b, c;

                    a = p.vecLength(p2, p1);

                    b = p.vecLength(p3, p1);

                    c = p.vecLength(p3, p2);

                    points[0] = 0;

                    points[1] = 0;

                    points[2] = 0;

                    points[3] = a;

                    points[4] = 0;

                    points[5] = 0;        

                    points[6] = (a * a + b * b - c * c) / 2 * a;

                    points[7] = Math.Sqrt(b * b - points[6] * points[6]);

                    points[8] = 0;

vecLength is a function I created to culculate the length of vectors.