form1.frm

大学里必学的数值分析

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   5985
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   8790
   LinkTopic       =   "Form1"
   ScaleHeight     =   5985
   ScaleWidth      =   8790
   StartUpPosition =   3  '窗口缺省
   Begin VB.TextBox Text1 
      Height          =   735
      Left            =   0
      TabIndex        =   5
      Top             =   360
      Width           =   2415
   End
   Begin VB.TextBox Text2 
      Height          =   735
      Left            =   2760
      TabIndex        =   4
      Top             =   360
      Width           =   2895
   End
   Begin VB.TextBox Text3 
      Height          =   615
      Left            =   240
      TabIndex        =   3
      Text            =   "计算PI的值"
      Top             =   1440
      Width           =   4335
   End
   Begin VB.CommandButton Command1 
      Caption         =   "计算 "
      Height          =   495
      Left            =   1680
      TabIndex        =   2
      Top             =   2400
      Width           =   3855
   End
   Begin VB.TextBox Text4 
      Appearance      =   0  'Flat
      Height          =   615
      Left            =   5880
      TabIndex        =   1
      Text            =   "10"
      Top             =   1440
      Width           =   1695
   End
   Begin VB.TextBox Text5 
      Height          =   735
      Left            =   6000
      TabIndex        =   0
      Top             =   360
      Width           =   2055
   End
   Begin VB.Label Label3 
      Caption         =   "节点数"
      Height          =   615
      Left            =   5040
      TabIndex        =   9
      Top             =   1440
      Width           =   855
   End
   Begin VB.Label Label4 
      Caption         =   "真实值"
      Height          =   375
      Left            =   6360
      TabIndex        =   8
      Top             =   0
      Width           =   1815
   End
   Begin VB.Label Label1 
      BackColor       =   &H0080C0FF&
      Caption         =   "梯形求积"
      BeginProperty Font 
         Name            =   "宋体"
         Size            =   15
         Charset         =   134
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   300
      Left            =   360
      TabIndex        =   7
      Top             =   0
      Width           =   1260
   End
   Begin VB.Label Label2 
      BackColor       =   &H0080C0FF&
      Caption         =   "抛物线求积"
      BeginProperty Font 
         Name            =   "宋体"
         Size            =   15
         Charset         =   134
         Weight          =   400
         Underline       =   0   'False
         Italic          =   0   'False
         Strikethrough   =   0   'False
      EndProperty
      Height          =   300
      Left            =   3120
      TabIndex        =   6
      Top             =   0
      Width           =   1620
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Command1_Click()
Dim n As Integer
Dim x As Double
Dim y1 As Double
Dim y2 As Double

Dim a As Double
Dim b As Double

Dim h As Double
Dim i As Integer



b = 1
a = 0
n = CInt(Text4.Text)

h = (b - a) / n
y1 = f(a) + f(b)
For i = 1 To n - 1
y1 = 2 * f(a + i * h) + y1
Next i
y1 = y1 * h * 2
Text1.Text = ccstr(y1)
Text5.Text = 3.14159265358


y2 = f(a) + f(b)
For i = 1 To n / 2
y2 = y2 + 4 * f(a + (2 * i - 1) * h)
Next i

For i = 1 To n / 2 - 1
y2 = y2 + 2 * f(a + 2 * i * h)
Next i
y2 = 4 * y2 * h / 3

Text2.Text = ccstr(y2)


End Sub
Function f(x As Double)
f = 1 / (x * x + 1)
End Function
Function ccstr(a As Double)


  If 0 < a And a < 1 Then ccstr = "0" + CStr(a) '特殊情况 为－1到1 之间的数字
  If -1 < a And a < 0 Then ccstr = "-0" + CStr(Abs(a))
  If CStr(a) = "0" Then ccstr = "0"
  If Abs(a) >= 1 Then ccstr = CStr(a)
End Function