System.Drawing.Graphics.DrawEllipticalArc C# (CSharp) Method

        internal void DrawEllipticalArc(double cx, double cy, double a, double b,
		                     double theta, double lambda1, double lambda2,
		                     bool isPieSlice)
        {
            this.cx = cx;
            this.cy = cy;
            this.a = a;
            this.b = b;
            this.theta = theta;
            this.isPieSlice = isPieSlice;

            // Angles in radians
            lambda1 = lambda1 * Math.PI / 180;
            lambda2 = lambda2 * Math.PI / 180;

            // Handle negative sweep angles
            if (lambda2 < 0)
            {
                var temp = lambda1;
                lambda1 += lambda2;
                lambda2 = temp;

            }
            else
                lambda2 += lambda1;

            eta1 = Math.Atan2(Math.Sin(lambda1) / b,
                              Math.Cos(lambda1) / a);
            eta2 = Math.Atan2(Math.Sin(lambda2) / b,
                              Math.Cos(lambda2) / a);
            cosTheta = Math.Cos(theta);
            sinTheta = Math.Sin(theta);

            // make sure we have eta1 <= eta2 <= eta1 + 2 PI
            eta2 -= twoPi * Math.Floor((eta2 - eta1) / twoPi);

            // the preceding correction fails if we have exactly et2 - eta1 = 2 PI
            // it reduces the interval to zero length
            if ((lambda2 - lambda1 > Math.PI) && (eta2 - eta1 < Math.PI))
            {
                eta2 += 2 * Math.PI;
            }

            computeFocii();

            // NOTE: Max degrees handled by the routine is 3
            drawEllipticalArcToContext(3, 0);
        }