VB寫出程式找出最大最小值

Question

題目是 f(x) = (X-1)(X+2) COS(4X)
X = -5 ~ 5 step 建議是0.001
需要標示的有 Ymax= ? X = ?
Ymin=? X=?

不知道從何下手!!! 希望知道的大大能盡速回答唷!!!

越簡單越好嚕!!!

應該是能用上function 吧!!!

電腦工程師 我把你用的寫進去

只是他出現 COS4 的名稱不對= =

希望你有看到我的補充 能盡快幫我解決問題!!!

謝謝!!!

Answer 1

Public Function Cos4(x As Single) As Single

Cos4 = (x - 1) * (x + 2) * Cos(4 * x)

End Function

Private Sub Command1_Click()
Dim x As Single, y As Single, tmp_x As Single, max As Single, min As Single, xa As Single, xi As Single

y = 0.001
x = -5 - y
max = -99
min = 99
Do
x = x + y
tmp_x = Cos4(x)
If (tmp_x > max) Then
max = tmp_x
xa = x
End If
If (tmp_x < min) Then
min = tmp_x
xi = x
End If
Loop While (x <= 5)

Print "X = " & xa & ", f(x) = " & max & " is max."
Print "X = " & xi & ", f(x) = " & min & " is min."

End Sub

2006-12-29 07:08:53 補充：
我再試了一次
沒看到你所說的問題啊

或者你把全部(3 個地方) 的 Cos4 改成 C4 試試看

如果有問題, 請來函討論. 不然, 我可能會錯失你再補充的疑點.

Answer 2

要簡單就不一定要傷腦筋, 加一個listbox在屬性欄sorted設成true
將你的資料全部丟到listbox就完成了,取listbox第一筆與最後一筆就是最小與最大值.

Answer 3

這還用不上 function 吧，當然也可以用
但如果前提要簡單，是應該不用

Private Type MaxMin
vMax As Double
x1 As Double
vMin As Double
x2 As Double
End Type

Private k As MaxMin

Private Sub Command1_Click()

Dim x As Double
Dim y As Double

For x = 5 To -5 Step -0.001

y = (x - 1) * (x + 2) * Cos(4 * x)

With k
If y > .vMax Then
.vMax = y: .x1 = x
ElseIf y < .vMin Then
.vMin = y: .x2 = x
End If

End With

Next
'
Debug.Print "YMax=" & k.vMax & vbTab & "X=" & k.x1
Debug.Print "YMin=" & k.vMin & vbTab & "X=" & k.x2

End Sub