On Thu, 23 Jun 2016 13:59:46 +1000, Steven D'Aprano wrote: > Given: > > x = INF > y = INF > assert x == y > > there is a reason to pick atan2(y, x) = pi/4: > > Since x == y, the answer should be the same as for any other pair of x == y. When x == y == 0, then atan2(y, x) is 0.