Definition talk:Angle Between Vectors

Is $0 \le \theta \le \pi$ a theorem or a definition, do you guys think? --GFauxPas 14:00, 19 March 2012 (EDT)
 * I think it's just a common convention, if I'm not mistaken. Abcxyz 14:05, 19 March 2012 (EDT)
 * Yes, it's a useful convention, but any $[2k\pi.. (2k+1)\pi]$ would work of course. --Lord_Farin 14:23, 19 March 2012 (EDT)