Need help with classifying triangles - scrpt mixes up acute and obtuse

[E1M1]

Does anyone know why my script mixes up acute and obtuse?

2nd test should be acute angle

3rd should be obtuse angle

expandcollapse popup

MsgBox(0,0,Test("1 0 2 0 1 2"))
MsgBox(0,0,Test("3 0 4 2 5 0"))
MsgBox(0,0,Test("6 0 7 0 8 2"))
;~ $TriangleCoords = "x1 xy x2 y2 x3 y3"
;~ Angles: If 1 of the angles are:
;         < 90 acute angle
;          > 90 obtuse angle
;         = 90 square corner
Func Test($TriangleCoords)
    ConsoleWrite(@CRLF)
 
    $Triangle = $TriangleCoords
    $Triangle = StringSplit($Triangle, " ")
 
    Dim $A[2], $B[2], $C[2], $AB[2], $BC[2], $CA[2]
 
    $A[0] = Number($Triangle[1])
    $A[1] = Number($Triangle[2])
 
    $B[0] = Number($Triangle[3])
    $B[1] = Number($Triangle[4])
 
    $C[0] = Number($Triangle[5])
    $C[1] = Number($Triangle[6])
 
    $AB[0] = $B[0] - $A[0]
    $AB[1] = $B[1] - $A[1]
 
    $BC[0] = $C[0] - $B[0]
    $BC[1] = $C[1] - $B[1]
 
    $CA[0] = $A[0] - $C[0]
    $CA[1] = $A[1] - $C[1]
 
    $ABLen = Sqrt($AB[0] ^ 2 + $AB[1] ^ 2)
    $BCLen = Sqrt($BC[0] ^ 2 + $BC[1] ^ 2)
    $CALen = Sqrt($CA[0] ^ 2 + $CA[1] ^ 2)
 
    If $ABLen = 0 Or $BCLen = 0 Or $CALen = 0 Then Return "ERROR"
 
 
    $pi = 3.14159265358979
    $radToDeg = 180 / $pi
 
 
    $BA_BC_Angle = Angle($AB,$BC)
    $AB_AC_Angle = Angle($AB,$CA)
    $CA_CB_angle = Angle($CA,$BC)
 
    ConsoleWrite($BA_BC_Angle&@CRLF)
    ConsoleWrite($AB_AC_Angle&@CRLF)
    ConsoleWrite($CA_CB_angle&@CRLF)
 
    If $BA_BC_Angle = 0 Or $AB_AC_Angle = 0 Or $CA_CB_angle = 0 Then Return "square corner"
 
    $BA_BC_Angle = ToTirstQuater(Abs(ACos($BA_BC_Angle) * $radToDeg))
    $AB_AC_Angle = ToTirstQuater(Abs(ACos($AB_AC_Angle) * $radToDeg))
    $CA_CB_angle = ToTirstQuater(Abs(ACos($CA_CB_angle) * $radToDeg))
 
    ConsoleWrite($BA_BC_Angle&@CRLF)
    ConsoleWrite($AB_AC_Angle&@CRLF)
    ConsoleWrite($CA_CB_angle&@CRLF)
 
    If $BA_BC_Angle < 90 and $AB_AC_Angle < 90 and $CA_CB_angle < 90 Then Return "acute angle"
 
    Return "obtuse angle"
EndFunc   ;==>Test
 
 
Func ScalarProduct($u,$v)
    Return $u[0]*$v[0] + $u[1]*$v[1]
EndFunc
 
Func Angle($u,$v)
    Return ScalarProduct($u,$v)/(Sqrt($u[0] ^ 2 + $u[1] ^ 2)*Sqrt($v[0] ^ 2 + $v[1] ^ 2))
EndFunc
 
Func ToTirstQuater($iAnge)
    If $iAnge > 90 Then Return 180 - $iAnge
    Return $iAnge
EndFunc

Pic shows triangles used in 3 tests

Edited October 9, 2011 by E1M1

[jaberwacky]

Edit: Actually, I now think the problem lies within this section of your code:

$AB[0] = $B[0] - $A[0]
$AB[1] = $B[1] - $A[1]
 
$BC[0] = $C[0] - $B[0]
$BC[1] = $C[1] - $B[1]
 
$CA[0] = $A[0] - $C[0]
$CA[1] = $A[1] - $C[1]

Well, no that can't be it because it correctly determines a right triangle. Ok, nevermind that and continue reading.

I think you're problem lies within this function: ToTirstQuater.

Here is my version of the code which, I believe, demonstrates the problem:

expandcollapse popup

MsgBox(0, 0, Test("1 0 2 0 1 2"))
MsgBox(0, 0, Test("3 0 5 0 4 2"))
MsgBox(0, 0, Test("6 0 7 0 8 2"))
 
;~ $TriangleCoords = "x1 y1 x2 y2 x3 y3"
;~ Angles: If 1 of the angles are:
;        < 90 acute angle
;         > 90 obtuse angle
;        = 90 square corner
 
Func Test($TriangleCoords)
    Local Const $Triangle = StringSplit($TriangleCoords, " ")
 
    Local $A[2]
    $A[0] = Number($Triangle[1])
    $A[1] = Number($Triangle[2])
 
    Local $B[2]
    $B[0] = Number($Triangle[3])
    $B[1] = Number($Triangle[4])
 
    Local $C[2]
    $C[0] = Number($Triangle[5])
    $C[1] = Number($Triangle[6])
 
    Local $AB[2]
    $AB[0] = $B[0] - $A[0]
    $AB[1] = $B[1] - $A[1]
 
    Local $BC[2]
    $BC[0] = $C[0] - $B[0]
    $BC[1] = $C[1] - $B[1]
 
    Local $CA[2]
    $CA[0] = $A[0] - $C[0]
    $CA[1] = $A[1] - $C[1]
 
    Local Const $ABLen = Sqrt($AB[0] ^ 2 + $AB[1] ^ 2)
    Local Const $BCLen = Sqrt($BC[0] ^ 2 + $BC[1] ^ 2)
    Local Const $CALen = Sqrt($CA[0] ^ 2 + $CA[1] ^ 2)
 
    If $ABLen = 0 Or $BCLen = 0 Or $CALen = 0 Then Return "ERROR"
 
    Local $BA_BC_Angle = Angle($AB, $BC)
    Local $AB_AC_Angle = Angle($AB, $CA)
    Local $CA_CB_Angle = Angle($CA, $BC)
 
    ConsoleWrite("-----------------------------------------" & @CRLF)
    ConsoleWrite("$BA_BC_Angle: " & $BA_BC_Angle & @CRLF)
    ConsoleWrite("$AB_AC_Angle: " & $AB_AC_Angle & @CRLF)
    ConsoleWrite("$CA_CB_Angle: " & $CA_CB_Angle & @CRLF & @CRLF)
    ConsoleWrite("Sum: " & $BA_BC_Angle + $AB_AC_Angle + $CA_CB_Angle & @CRLF)
 
    If $BA_BC_Angle = 90 Or $AB_AC_Angle = 90 Or $CA_CB_Angle = 90 Then
        ConsoleWrite("-----------------------------------------" & @CRLF & @CRLF)
        Return "square corner"
    EndIf
 
    $BA_BC_Angle = ToTirstQuater($BA_BC_Angle)
    $AB_AC_Angle = ToTirstQuater($AB_AC_Angle)
    $CA_CB_Angle = ToTirstQuater($CA_CB_Angle)
 
    ConsoleWrite(@CRLF & "$BA_BC_Angle: " & $BA_BC_Angle & @CRLF)
    ConsoleWrite("$AB_AC_Angle: " & $AB_AC_Angle & @CRLF)
    ConsoleWrite("$CA_CB_Angle: " & $CA_CB_Angle & @CRLF & @CRLF)
    ConsoleWrite("Sum: " & $BA_BC_Angle + $AB_AC_Angle + $CA_CB_Angle & @CRLF)
    ConsoleWrite("-----------------------------------------" & @CRLF & @CRLF)
 
    If $BA_BC_Angle > 90 Or $AB_AC_Angle > 90 Or $CA_CB_Angle > 90 Then Return "obtuse angle"
 
    If $BA_BC_Angle < 90 And $AB_AC_Angle < 90 And $CA_CB_Angle < 90 Then Return "acute angle"
EndFunc   ;==>Test
 
Func dot_product($v, $u)
    Return $v[0] * $u[0] + $v[1] * $u[1]
EndFunc   ;==>ScalarProduct
 
Func angle($v, $u)
    Local Const $dot_product = dot_product($v, $u)
    Local Const $length_of_v = Sqrt($v[0] ^ 2 + $v[1] ^ 2)
    Local Const $length_of_u = Sqrt($u[0] ^ 2 + $u[1] ^ 2)
    Local Const $cos_theta = ($dot_product / ($length_of_v * $length_of_u))
    Return Round(ACos($cos_theta) * (180 / 3.14159265358979), 3)
EndFunc
 
Func ToTirstQuater($iAnge)
    If $iAnge > 90 Then Return Abs(180 - $iAnge)
    Return Abs($iAnge)
EndFunc   ;==>ToTirstQuater

This has been a lot of fun. I've learned more about trigonometry than I ever learned in school.

Edited October 11, 2011 by LaCastiglione