System.Drawing.Drawing2D.GraphicsPath.AppendArc C# (CSharp) Method

        void AppendArc(bool start, float x, float y, float width, float height, float startAngle, float endAngle)
        {
            float delta, bcp;
            float sin_alpha, sin_beta, cos_alpha, cos_beta;

            float rx = width / 2;
            float ry = height / 2;

            /* center */
            float cx = x + rx;
            float cy = y + ry;

            /* angles in radians */
            float alpha = (float)(startAngle * Math.PI / 180);
            float beta = (float)(endAngle * Math.PI / 180);

            /* adjust angles for ellipses */
            alpha = (float) Math.Atan2 (rx * Math.Sin (alpha), ry * Math.Cos (alpha));
            beta = (float) Math.Atan2 (rx * Math.Sin (beta), ry * Math.Cos (beta));

            if (Math.Abs (beta - alpha) > Math.PI){
                if (beta > alpha)
                    beta -= (float) (2 * Math.PI);
                else
                    alpha -= (float) (2 * Math.PI);
            }

            delta = beta - alpha;
            // http://www.stillhq.com/ctpfaq/2001/comp.text.pdf-faq-2001-04.txt (section 2.13)
            bcp = (float)(4.0 / 3 * (1 - Math.Cos (delta / 2)) / Math.Sin (delta / 2));

            sin_alpha = (float)Math.Sin (alpha);
            sin_beta = (float)Math.Sin (beta);
            cos_alpha = (float)Math.Cos (alpha);
            cos_beta = (float)Math.Cos (beta);

            // move to the starting point if we're not continuing a curve
            if (start) {
                // starting point
                float sx = cx + rx * cos_alpha;
                float sy = cy + ry * sin_alpha;
                Append (sx, sy, PathPointType.Line, false);
            }

            AppendBezier (cx + rx * (cos_alpha - bcp * sin_alpha),
                      cy + ry * (sin_alpha + bcp * cos_alpha),
                      cx + rx * (cos_beta  + bcp * sin_beta),
                      cy + ry * (sin_beta  - bcp * cos_beta),
                      cx + rx *  cos_beta,
                      cy + ry *  sin_beta);
        }