将角度换算为弧度

        /// <summary>
        /// 将角度换算为弧度。
        /// </summary>
        /// <param name="degrees">角度</param>
        /// <returns>弧度</returns>
        public static double ConvertDegreesToRadians(double degrees)
        {
            return degrees * Math.PI / 180;
        }

        public double HaverSin(double theta)
        {
            var v = Math.Sin(theta / 2);
            return v * v;
        }