I'm not very good at doing things the easy (translate: smart) way, so here's
the brute-force approach.
It's in a function so it should be plug-n-play for you.
Disclaimer: I made every effort to be correct, but do not design any
100-story buildings using this code until this function has been tested to
YOUR satisfaction. You bear all responsibility for the use of this code,
including, but not limited to, structural collapse, explosion,
dismemberment, death, tornado, unintentional nuclear war.
James
Sub test_atn()
Debug.Print better_Atn(0, 0) * 180 / 3.14
Debug.Print better_Atn(1, -1) * 180 / 3.14
End Sub
Function better_Atn(deltaY1 As Double, deltaX1 As Double)
Dim PI As Double: PI = 4 * Atn(1)
Dim calcAngle As Double
If deltaX1 = 0 Then
'on vertical axis
If deltaY1 > 0 Then
calcAngle = PI / 2
ElseIf deltaY1 < 0 Then
calcAngle = 3 / 2 * PI
Else 'deltaX1 = 0 and deltaY1 = 0
MsgBox "Zero-length vector. " & _
"Angle can not be determined. You " & _
"should have the function throw an error here."
End If
ElseIf deltaX1 > 0 Then
'quadrants I and IV
If deltaY1 >= 0 Then 'quadrant I
calcAngle = Atn(deltaY1 / deltaX1)
Else 'quadrant IV
calcAngle = 2 * PI + Atn(deltaY1 / deltaX1)
End If
ElseIf deltaX1 < 0 Then
'quadrants II and III
calcAngle = PI + Atn(deltaY1 / deltaX1)
End If
better_Atn = calcAngle
End Function
