A. 在acrgis中使用VB編寫的一個程序，功能是計算多邊形面積，出了點問題，請高手解答
Rem 凸n變形可以看成是n-1個三角形的面積
Rem 三角形的面積S=sqr(p*(p-a)*(p-b)*(p-c))，其中，p=(a+b+c)/2，a、b、c為邊長，邊長=sqr((x1-x2)^2+(y1-y2)^2)，而(x1,y1)和(x2,y2)分別為兩點的坐標值
Rem 以下代碼為求任意多邊形的面積，邊數由用戶自行決定
Private Sub Command1_Click()
Dim n, s, i, x(), y(), a, b, c, p
k:
n = Int(Val(Trim(InputBox("請輸入多邊形的邊數：", "多邊形面積", 3))))
If n < 3 Then MsgBox "邊數必須≥3！請重試！", , "多邊形面積": GoTo k
On Error Resume Next
ReDim x(1 To n), y(1 To n)
s = 0
For i = 1 To n
x(i) = Val(Trim(InputBox("請輸入" & IIf(n = 3, "三角形", n & "邊形") & "第" & i & "個點的橫坐標:")))
y(i) = Val(Trim(InputBox("請輸入" & IIf(n = 3, "三角形", n & "邊形") & "第" & i & "個點的橫坐標:")))
If i > 1 Then Line (x(i), y(i))-(x(i - 1), y(i - 1))
Next
For i = 2 To n - 1
a = Sqr((x(1) - x(i)) ^ 2 + (y(1) - y(i)) ^ 2)
b = Sqr((x(1) - x(i + 1)) ^ 2 + (y(1) - y(i + 1)) ^ 2)
c = Sqr((x(i) - x(i + 1)) ^ 2 + (y(i) - y(i + 1)) ^ 2)
p = (a + b + c) / 2
s = s + Sqr(p * (p - a) * (p - b) * (p - c))
Next
MsgBox IIf(n = 3, "三角形", n & "邊形") & "面積是" & s, , "多邊形面積"
End Sub
B. 用海倫公式求三角形面積，怎麼用VB編成程序語句都是啥
Private Sub Form_Load()
On Error GoTo skip
1:
Dim a(1 To 3) As IntegerFor i = 1 To 3
a(i) = InputBox("請輸入第" & i & "條邊的邊長", "三角形的面積")
Next i
Dim s, p As Integer
p = (a(1) + a(2) + a(3)) / 2
If p > a(1) And p > a(2) And p > a(3) Then
s = Sqr(p * (p - a(1)) * (p - a(2)) * (p - a(3)))
MsgBox "邊長為【" & a(1) & "】【" & a(2) & "】【" & a(3) & "】的三角形面積是：" & s
End
Else
x = MsgBox("輸入的值【" & a(1) & "】【" & a(2) & "】【" & a(3) & "】不能構成三角形！是否重新輸入？", vbYesNo)
If x = vbYes Then
GoTo 1
Else
End
End If
End If
skip:
If Err.Number = 13 Then
MsgBox "輸入錯誤！請檢查！", vbOKOnly, "注意！"
End
End If
End Sub