根据下面的公式，求π

精确到小数后6位。

代码1

Private Sub Command1_Click()    Dim pai As Double, i As Double, item As Double    pai = 0    i = 1    item = 1    Do While item >= 0.000001        pai = pai + (-1) ^ (i - 1) * item        i = i + 1        item = 1 / (2 * i - 1)    Loop    Label2.Caption = Str(4 * pai)End Sub

代码2

Private Sub Command1_Click()    Dim pai As Double, item As Double, i As Double    Dim sign As Integer    pai = 0    i = 1    sign = 1    item = 1    Do While item >= 0.000001        pai = pai + sign * item        sign = sign * -1        i = i + 2        item = 1 / i    Loop    Label2.Caption = Str(4 * pai)End Sub

代码3

Private Sub Command1_Click()    Dim pai As Double, item As Double, i As Double    Dim sign As Integer    pai = 1    i = 1    sign = 1    item = 1    Do While item >= 0.000001        sign = sign * -1        i = i + 2        item = 1 / i        pai = pai + sign * item    Loop    Label2.Caption = Str(4 * pai)End Sub