My VBA code for integration (Trapezoidal as approximation of area)

Sub Trapeziodal()
Sheets("Sheet2").Select
Dim integral As Double, delta As Double, start As Double, last As Double
Dim n As Integer
start = 0
n = 10
last = 1
delta = (last - start) / n
integral = 0
For i = 1 To n
integral = integral + 0.5 * delta * (fval(start + (i - 1) * delta) + fval(start + (i * delta)))


Next
Cells(1, 1) = integral
End Sub