定积分.frm

Visual Basic课程举例1 有很好的例题

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "计算定积分"
   ClientHeight    =   5100
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   7485
   LinkTopic       =   "Form1"
   ScaleHeight     =   5100
   ScaleWidth      =   7485
   StartUpPosition =   3  '窗口缺省
   Begin VB.TextBox Text3 
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   4080
      TabIndex        =   8
      Text            =   "1000"
      Top             =   2760
      Width           =   1575
   End
   Begin VB.CommandButton Command1 
      Caption         =   "计算积分"
      BeginProperty Font 
         Name            =   "宋体"
         Size            =   18
         Charset         =   134
         Weight          =   700
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   615
      Left            =   1500
      TabIndex        =   5
      Top             =   4320
      Width           =   2175
   End
   Begin VB.TextBox Text2 
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   1560
      TabIndex        =   4
      Text            =   "2.11017302797178 "
      Top             =   2040
      Width           =   4035
   End
   Begin VB.TextBox Text1 
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   1560
      TabIndex        =   3
      Text            =   "-1.07999135356475 "
      Top             =   1320
      Width           =   4035
   End
   Begin VB.Label lblResult 
      AutoSize        =   -1  'True
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   1980
      TabIndex        =   9
      Top             =   3360
      Width           =   120
   End
   Begin VB.Label Label5 
      AutoSize        =   -1  'True
      Caption         =   "积分结果"
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   60
      TabIndex        =   7
      Top             =   3480
      Width           =   1440
   End
   Begin VB.Label Label4 
      AutoSize        =   -1  'True
      Caption         =   "输入积分精度(以次数计)"
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   60
      TabIndex        =   6
      Top             =   2760
      Width           =   3870
   End
   Begin VB.Label Label3 
      AutoSize        =   -1  'True
      Caption         =   "输入b"
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   240
      TabIndex        =   2
      Top             =   1920
      Width           =   960
   End
   Begin VB.Label Label2 
      AutoSize        =   -1  'True
      Caption         =   "输入a"
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   495
      Left            =   240
      TabIndex        =   1
      Top             =   1200
      Width           =   960
   End
   Begin VB.Label Label1 
      Caption         =   "计算f(x)=Sin(x)*2+3*Cos(x/5)-x^2在给定区间的定积分"
      BeginProperty Font 
         Name            =   "Arial Black"
         Size            =   18
         Charset         =   0
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   1095
      Left            =   240
      TabIndex        =   0
      Top             =   120
      Width           =   6885
      WordWrap        =   -1  'True
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Option Explicit
DefDbl A-B, F, H, S, X
Private Sub Command1_Click()
    Dim n As Integer, i As Integer, a, b, f, h, s, x
    a = Val(Text1)
    b = Val(Text2)
    n = Val(Text3)
    h = (b - a) / n
    s = 0
    x = a
    For i = 1 To n
        f = Sin(x) * 2 + 3 * Cos(x / 5) - x ^ 2
        s = s + h * f
        x = x + h
    Next i
    lblResult.Caption = s
    Debug.Print s
End Sub