求二次方程的最小值和最大值

如何使用c#找到二次方程的最小值和最大值

f(x,y) = x^2 + y^2 + 25 * (sin(x)^2 + sin(y)^2) ,where (x,y) from (-2Pi, 2Pi) ??

在手动求解中，我得到的最小值=0，最大值=8Pi^2=78.957.

我试图基于线性二次码编写代码，但出现了完全错误这个代码给出min=-4。？？并且max=96，你能帮我知道我的错误在哪里吗？？

我把代码上传到dropbox，如果有人可以看的话：https://www.dropbox.com/s/p7y6krk2gk29i9e/Program.cs

    double[] X, Y, Result; // Range array and result array.
    private void BtnRun_Click(object sender, EventArgs e)
    {
        //Set any Range for the function
        X = setRange(-2 * Math.PI, 2 * Math.PI, 10000);
        Y = setRange(-2 * Math.PI, 2 * Math.PI, 10000);
        Result = getOutput_twoVariablesFunction(X, Y);
        int MaxIndex = getMaxIndex(Result);
        int MinIndex = getMinIndex(Result);
        TxtMin.Text = Result[MinIndex].ToString();
        TxtMax.Text = Result[MaxIndex].ToString();
    }
    private double twoVariablesFunction(double x,double y)
    {
        double f;
        //Set any two variables function
        f = Math.Pow(x, 2) + Math.Pow(y, 2) + 25 * (Math.Pow(Math.Sin(x), 2) + Math.Pow(Math.Sin(y), 2));
        return f;
    }
    private double[] setRange(double Start, double End, int Sample)
    {
        double Step = (End - Start) / Sample;
        double CurrentVaue = Start;
        double[] Array = new double[Sample];
        for (int Index = 0; Index < Sample; Index++)
        {
            Array[Index] = CurrentVaue;
            CurrentVaue += Step;
        }
        return Array;
    }
    private double[] getOutput_twoVariablesFunction(double[] X, double[] Y)
    {
        int Step = X.Length;
        double[] Array = new double[Step];
        for (int Index = 0; Index < X.Length ; Index++)
        {
            Array[Index] = twoVariablesFunction(X[Index], Y[Index]);
        }
        return Array;
    }
    private int getMaxIndex(double[] ValuesArray)
    {
        double M = ValuesArray.Max();
        int Index = ValuesArray.ToList().IndexOf(M);
        return Index;
    }
    private int getMinIndex(double[] ValuesArray)
    {
        double M = ValuesArray.Min();
        int Index = ValuesArray.ToList().IndexOf(M);
        return Index;
    }