复杂方程可以自己定义，以下是看别人的题目，然后自己来做

以下是计算结果

private void GetMinResult(out double resultX1, out double min)
        {
            double x1, result;
            Random random1 = new Random(DateTime.Now.Millisecond* DateTime.Now.Second);
            min = 999999;
            resultX1 = 0;
            for (int i = 0; i < 654321; i++)
            {
                if (random1.Next(0, 100) % 2 == 0)
                {
                    x1 = resultX1 + random1.NextDouble()*100;

                }
                else
                {
                    x1 = resultX1 - random1.NextDouble()*100;
                }
                if (x1 < 0 || x1 > 50)
                {
                    continue;
                }
                result = x1 * Math.Sin(x1) * Math.Cos(2 * x1) - 2 * x1 * Math.Sin(3 * x1) + 3 * x1 * Math.Sin(4 * x1);
                if (result < min)
                {
                    resultX1 = x1;
                    min = result;
                }
            }
        }