B4J Question (math) calculating an integral

Sub AppStart (Args() As String)
    Log(CalcIntegral(-10000, 5000))
End Sub

Private Sub CalcIntegral(FromValue As Double, ToValue As Double) As Double
    Dim u As Double = 10
    Dim o As Double = 64
    Dim e2 As Double = Power(cE, -1/2)
    Dim denominator As Double = Sqrt(2 * cPI * o)
    Dim delta As Double = 0.001
    Dim Result As Double = 0 'C
    Dim t as Double
    For t = FromValue To ToValue Step delta
        Dim i As Double = Power(e2, Power((t - u) / o, 2)) / denominator
'        Log(i)
        Result = Result + i * delta
    Next
    Return Result
End Sub

 Result = Result + i * delta

'Normal distribution integral
'BeginValue and EndValue are the interval values
'Mu = mean value
'Sigma = standard deviation
'Delta = calculation interval
Private Sub CalcGaussIntegral(BeginValue As Double, EndValue As Double, Mu As Double, Sigma As Double, Delta As Double) As Double
    Private i, Integral, y0, y1 As Double
    Private Denominator As Double
  
    Delta = 0.1
    Denominator = Sqrt(2 * cPI)
    y0 = Power(cE, -(BeginValue - Mu) * (BeginValue - Mu) / 2 / Sigma / Sigma) / Sigma / Denominator
  
    For i = BeginValue + Delta To EndValue Step Delta
        y1 = Power(cE, -(i - Mu) * (i - Mu) / 2 / Sigma / Sigma) / Sigma / Denominator
        Integral = Integral + (y0 + y1) / 2 * Delta
        y0 = y1
    Next
    Return Integral
End Sub