用vb.net在Label控件上绘制方程式y＝e⁻ˣcos（x）的函数曲线

可以使用`System.Drawing`命名空间下的`Graphics`类，在`Label`控件的`Paint`事件中绘制函数曲线。具体代码如下：

Private Sub Label1_Paint(sender As Object, e As PaintEventArgs) Handles Label1.Paint
    Dim g As Graphics = e.Graphics
    Dim pen As Pen = New Pen(Color.Blue, 2)
    Dim scale As Integer = 50
    Dim xMax As Integer = Label1.Width / scale
    Dim yMax As Integer = Label1.Height / scale
    Dim xMin As Integer = -xMax
    Dim yMin As Integer = -yMax
    Dim xRange As Integer = xMax - xMin
    Dim yRange As Integer = yMax - yMin
    Dim xscale As Single = Label1.Width / xRange
    Dim yscale As Single = Label1.Height / yRange

    For i As Integer = 0 To Label1.Width Step scale
        g.DrawLine(Pens.LightGray, i, 0, i, Label1.Height)
    Next

    For i As Integer = 0 To Label1.Height Step scale
        g.DrawLine(Pens.LightGray, 0, i, Label1.Width, i)
    Next

    g.TranslateTransform(Label1.Width / 2, Label1.Height / 2)

    Dim x1, y1, x2, y2 As Single

    x1 = xMin
    y1 = Math.Exp(-x1) * Math.Cos(x1)
    y1 = CSng(y1 * yscale)
    x1 = CSng(x1 * xscale)

    For i As Integer = xMin + 1 To xMax Step 1
        x2 = i
        y2 = Math.Exp(-x2) * Math.Cos(x2)
        y2 = CSng(y2 * yscale)
        x2 = CSng(x2 * xscale)

        g.DrawLine(pen, x1, y1, x2, y2)

        x1 = x2
        y1 = y2
    Next
End Sub

在代码中，我们先定义了绘制曲线所需的变量和参数，其中`scale`表示坐标轴上的刻度间距，`xMax`和`yMax`表示坐标轴的最大值，`xMin`和`yMin`表示坐标轴的最小值，`xRange`和`yRange`表示坐标轴的范围，`xscale`和`yscale`表示坐标轴的比例尺。

然后使用两个`For`循环绘制坐标轴上的刻度线。

最后在坐标系中绘制函数曲线。我们使用`Math.Exp`和`Math.Cos`函数计算出每个点的坐标，然后将其转换为屏幕坐标系中的坐标。使用`DrawLine`方法绘制曲线。