A. 在acrgis中使用VB编写的一个程序，功能是计算多边形面积，出了点问题，请高手解答
Rem 凸n变形可以看成是n-1个三角形的面积
Rem 三角形的面积S=sqr(p*(p-a)*(p-b)*(p-c))，其中，p=(a+b+c)/2，a、b、c为边长，边长=sqr((x1-x2)^2+(y1-y2)^2)，而(x1,y1)和(x2,y2)分别为两点的坐标值
Rem 以下代码为求任意多边形的面积，边数由用户自行决定
Private Sub Command1_Click()
Dim n, s, i, x(), y(), a, b, c, p
k:
n = Int(Val(Trim(InputBox("请输入多边形的边数：", "多边形面积", 3))))
If n < 3 Then MsgBox "边数必须≥3！请重试！", , "多边形面积": 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("请输入" & IIf(n = 3, "三角形", n & "边形") & "第" & i & "个点的横坐标:")))
y(i) = Val(Trim(InputBox("请输入" & IIf(n = 3, "三角形", n & "边形") & "第" & i & "个点的横坐标:")))
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 & "边形") & "面积是" & s, , "多边形面积"
End Sub
B. 用海伦公式求三角形面积，怎么用VB编成程序语句都是啥
Private Sub Form_Load()
On Error GoTo skip
1:
Dim a(1 To 3) As IntegerFor i = 1 To 3
a(i) = InputBox("请输入第" & i & "条边的边长", "三角形的面积")
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 "边长为【" & a(1) & "】【" & a(2) & "】【" & a(3) & "】的三角形面积是：" & s
End
Else
x = MsgBox("输入的值【" & a(1) & "】【" & a(2) & "】【" & a(3) & "】不能构成三角形！是否重新输入？", vbYesNo)
If x = vbYes Then
GoTo 1
Else
End
End If
End If
skip:
If Err.Number = 13 Then
MsgBox "输入错误！请检查！", vbOKOnly, "注意！"
End
End If
End Sub