Re: Re: Re: Simplifying ArcTan

*To*: mathgroup at smc.vnet.net*Subject*: [mg55613] Re: [mg55567] Re: [mg55542] Re: [mg55526] Simplifying ArcTan*From*: DrBob <drbob at bigfoot.com>*Date*: Thu, 31 Mar 2005 01:24:12 -0500 (EST)*References*: <200503300821.DAA21790@smc.vnet.net>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

> ArcTan[Cos[x],Sin[x]] == x The RHS function is one-to-one, but the LHS is periodic in x. They only agree on an interval. Bobby On Wed, 30 Mar 2005 03:21:00 -0500 (EST), David Park <djmp at earthlink.net> wrote: > But why this restriction? I thought the whole point of the two argument > ArcTan was that it covered the entire circle, taking signs into account. The > two argument ArcTan is a great idea that is incorporated into Mathematica. > It would be even greater if Simplify knew the identity... > > ArcTan[Cos[x],Sin[x]] == x > > Is there any reason that should not be true? > > David Park > djmp at earthlink.net > http://home.earthlink.net/~djmp/ > > > From: Bob Hanlon [mailto:hanlonr at cox.net] To: mathgroup at smc.vnet.net > To: mathgroup at smc.vnet.net > > > Simplify[ArcTan[Cos[x],Sin[x]],0<=x<Pi/2] > > x > > > Bob Hanlon > > > > > > -- DrBob at bigfoot.com

**References**:**Re: Re: Simplifying ArcTan***From:*"David Park" <djmp@earthlink.net>