如何计算一函数的积分值

[superwxh]

请问如何用vb编写一个计算函数积分的程序。我的问题是求∫F(x)dx 此处x为（0，25） f(x)=λ^(-(x-u)^2/(2*a^2))/a*sqrt(2π)

[zqfleaf]

先取步长dx=0.1(根据精度需要）
x0=0
x=25
x1=x0
s=0
for x1=x0+dx to x step dx
s=s + (f(x1-dx)+ f(x1))*dx/2
next
dx取值越小，s的结果越正确

[liu584]

用梯形的逐次分半法
Dim i As Long
Dim n As Long
Dim h As Double
Dim T0 As Double
Dim T As Double
Dim F As Double
Dim Distant As Double
n = 1
h = (Unum - Lnum) / 2
T0 = h * f(0)+ f(25)
Do
F = 0
For i = 1 To n
F = F + f(2 * i - 1) * h)
Next i
T = T0 / 2 + h * F
Distant = T - T0
'为下一次做准备
n = 2 * n
h = h / 2
T0 = T
Loop While (Abs(Distant) > 3 * ExpectError)
Answer= T
其中ExpectError是需要的精度。