Rectangle's coordinates

[MarkT]

This is what I came up with real quick. See if it gives you some ideas.

'   Define Corners 1, 2, 3, and 4
'   Find the lengths of
'       Side 1_2
'       Side 2_3
'       Side 3_4
'       Side 4_1
'       Diagonal 1_3
'       Diagonal 2_4
'
'   1-----------2
'   |           |
'   |           |
'   |           |
'   4-----------3
'
'   If Side 1_2 = Side 3_4 and Side 4_1 = Side 2_3 Then
'       Either Square, parallagram or Rectangle
'   If Diagonal 1_3 = Diagonal 2_4 Then Rectangle or Square
'       Else parallagram
Option Explicit
 
Private Type Corners
    X As Integer
    Y As Integer
End Type
 
Dim Corner(1 To 4) As Corners
Dim Side(1 To 4) As Single
Dim Diagonal(1) As Single
 
Private Sub Form_Load()
 
    Me.AutoRedraw = True
    Me.Show
    
'   Define the corners of the rectangle
    Corner(1).X = 400
    Corner(1).Y = 400
    
    Corner(2).X = 2400
    Corner(2).Y = 200
    
    Corner(3).X = 2500
    Corner(3).Y = 1200
    
    Corner(4).X = 500
    Corner(4).Y = 1400
    
'   Draw the rectangle
    Me.Line (Corner(1).X, Corner(1).Y)-(Corner(2).X, Corner(2).Y)
    Me.Line -(Corner(3).X, Corner(3).Y)
    Me.Line -(Corner(4).X, Corner(4).Y)
    Me.Line -(Corner(1).X, Corner(1).Y)
    
'   Get the length of each side
    Side(1) = GetLength(Corner(1), Corner(2)) ' Side 1_2
    Side(2) = GetLength(Corner(3), Corner(4)) ' Side 3_4
    Side(3) = GetLength(Corner(2), Corner(3)) ' Side 2_3
    Side(4) = GetLength(Corner(4), Corner(1)) ' Side 4_1
    
'   Get Diagonal Lengths
    Diagonal(0) = GetLength(Corner(1), Corner(3))
    Diagonal(1) = GetLength(Corner(2), Corner(4))
    
End Sub
 
Private Function GetLength(FirstCorner As Corners, SecondCorner As Corners) As Single
Dim A As Long
Dim B As Long
Dim C As Long
 
 
    A = Abs(FirstCorner.X - SecondCorner.X)
    B = Abs(FirstCorner.Y - SecondCorner.Y)
    
    C = A ^ 2 + B ^ 2
    
    GetLength = Sqr(C)
    
End Function