gogotanaka/ruby — pull request #1 by gogotanaka (2014-09-07 23:24:17+00:00)
Title: Implement math.phi

https://github.com/ruby/ruby/commit/b160d23c68e2e8fcd82b96fab0977be11c2b9ec6

https://github.com/ruby/ruby/commit/14373fc4db7440d39db4fd39297f2ed44cc990f2

こちらを参考にさせていただきました.