erlang/otp — pull request #106 by asterite (2013-10-16 18:02:13+00:00)
Title: Spec for atan2 should be atan2(Y, X), not atan2(X, Y)

math:atan2 receives Y and X as arguments, but the spec here ( http://www.erlang.org/doc/man/math.html ) says atan2(X, Y). I guess that comes from the file changed in this commit.