public void ExternalAngleConstraintShouldWork() { for (int i = 1; i < 10; i++) { var line1 = new Line( new Point(0, 0, false), new Point(10, 0, false, true) ); var line2 = new Line( new Point(0, 0, false), new Point(10, -1, false) ); Console.WriteLine(i); var a = Math.PI / 2 / 3; SketchSolve.Solver.solve (true , line1.HasExternalAngle(line2, new Parameter(a, false))); line1 .Vector .Cosine(line2.Vector) .Should() .BeApproximately(Math.Cos(Math.PI - a), 0.001); } }