Relative angle between 2 vectors

Well, you could replace all the if's with simply the difference between atan(y1,x1)-atan(y2,x2). This is basically what it says in the first post. It will work, if you keep the difference between the angles small enough. However if one angle is 359 and the other 10, it will take the longest route instead of the shortest:

Graphics 800, 600, 0, 2
SetBuffer BackBuffer()

ang1# = Rand(360)
ang2# = Rand(360)
ang2r# = ang2#

Repeat
	
	;draw angles
	Cls
	Origin 400, 300

	;red=angle1	
	Color 255, 0, 0
	x1# = Cos(ang1) * 120
	y1# = Sin(ang1) * 120
	Line 0, 0, x1, y1
	Text x1 * 1.2, y1 * 1.2, ang1, 1, 1
	
	;aqua=angle2
	Color 0, 255, 255
	x2# = Cos(ang2) * 120
	y2# = Sin(ang2) * 120
	Line 0, 0, x2, y2
	Text x2 * 1.2, y2 * 1.2, ang2, 1, 1
	
	Origin 0, 0

;-----------------------------------------------------------------------------
	;calculate angles from coordinates
	Color 255, 255, 255
	angle1# = ATan2(y1, x1); + 360) Mod 360
	angle2# = ATan2(y2, x2); + 360) Mod 360
	
	;calculate differences
	angdif# = (angle2 - angle1)
;-----------------------------------------------------------------------------

	;show difference
	Text 0, 100, "difference= " + angdif#
	
	;show usage
	Text 0, 0, "usage:"
	Text 0, 20, "use cursor keys to move angle1, use space to apply difference"

	;cursor keys = move angle 1
	If KeyDown(203) Then ang1 = ang1 - 1
	If KeyDown(205) Then ang1 = ang1 + 1
	
	;automove with space
	If KeyHit(57) Then
		ang2r# = angle2 - angdif
	End If	
	If ang2r <> ang2 Then ang2 = ang2 + Sgn(ang2r - ang2)	
	

	Flip

Until KeyHit(1)
WaitKey()

End

edit: I removed the "Mod 360"'s and it seems to be a bit better