form1.frm

大学里必学的一门课程

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   5205
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   6885
   LinkTopic       =   "Form1"
   ScaleHeight     =   5205
   ScaleWidth      =   6885
   StartUpPosition =   3  '窗口缺省
   Begin VB.TextBox Text7 
      Height          =   495
      Left            =   3240
      TabIndex        =   7
      Text            =   "原函数为y=exp(-x)"
      Top             =   240
      Width           =   3615
   End
   Begin VB.CommandButton Command1 
      Caption         =   "计算公式和对应的y值"
      Height          =   3015
      Left            =   3360
      TabIndex        =   6
      Top             =   1800
      Width           =   495
   End
   Begin VB.TextBox Text6 
      Height          =   855
      Left            =   4080
      TabIndex        =   5
      Top             =   2760
      Width           =   2775
   End
   Begin VB.TextBox Text5 
      Height          =   855
      Left            =   4080
      TabIndex        =   4
      Top             =   1440
      Width           =   2775
   End
   Begin VB.TextBox Text4 
      Height          =   855
      Left            =   360
      TabIndex        =   3
      Top             =   3600
      Width           =   2535
   End
   Begin VB.TextBox Text3 
      Height          =   855
      Left            =   360
      TabIndex        =   2
      Top             =   2280
      Width           =   2415
   End
   Begin VB.TextBox Text2 
      Height          =   855
      Left            =   360
      TabIndex        =   1
      Top             =   1200
      Width           =   2415
   End
   Begin VB.TextBox Text1 
      Height          =   855
      Left            =   360
      TabIndex        =   0
      Top             =   120
      Width           =   2415
   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 x0 As Double
Dim x1 As Double
Dim x2 As Double
Dim y0 As Double
Dim y1 As Double
Dim y2 As Double
Dim x As Double
Dim y As Double

Dim s0 As String
Dim s1 As String
Dim s2 As String


Dim t0 As Double
Dim t1 As Double
Dim t2 As Double
 
x0 = CDbl(Text1.Text)
x1 = CDbl(Text2.Text)
x2 = CDbl(Text3.Text)
x = CDbl(Text4.Text)
y1 = Exp(-x1)
y2 = Exp(-x2)
y0 = Exp(-x0)

t0 = (x - x1) * (x - x2) / ((x0 - x1) * (x0 - x2))
t1 = (x - x0) * (x - x2) / ((x1 - x0) * (x1 - x2))
t2 = (x - x0) * (x - x1) / ((x2 - x0) * (x2 - x1))
y = y1 * t1 + y2 * t2 + y0 * t0

Text5.Text = ccstr(y)
s0 = "(x-" + ccstr(x1) + ")" + "*" + "(x-" + ccstr(x2) + ")" + "/(" + ccstr((x0 - x1) * (x0 - x2)) + ")"
s1 = "(x-" + ccstr(x2) + ")" + "*" + "(x-" + ccstr(x0) + ")" + "/(" + ccstr((x1 - x2) * (x1 - x0)) + ")"
s2 = "(x-" + ccstr(x1) + ")" + "*" + "(x-" + ccstr(x0) + ")" + "/(" + ccstr((x2 - x1) * (x2 - x0)) + ")"

Text6.Text = s0 + "*" + ccstr(y0) + "+" + s1 + "*" + ccstr(y1) + s2 + "*" + ccstr(y2)

End Sub
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