Re: using answer form reduce

*To*: mathgroup at smc.vnet.net*Subject*: [mg68633] Re: using answer form reduce*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Mon, 14 Aug 2006 06:44:05 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <ebmtf5$6fb$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

akil wrote: > After using reduce I get the following two types of answers: > > answer == Real1 || answer == Real2 > or > answer == Real3 > , the type can change from one formula to another. > > I need the Reals, and put them all in a list. The problem is getting all the > reals, without knowing which type I deal with, it should be able to be done > fast. > > I tried making a list of the returned adres, and then using > Cases[list, _Real, Infinity] and using Select[list,NumericQ] but both do not > give me the answer I require. > > How can I get the answer I require e.g. something like {Real1,Real2,Real3} What about the following? sols = Reduce[x^4 == 4] --> x == -Sqrt[2] || x == (-I)*Sqrt[2] || x == I*Sqrt[2] || x == Sqrt[2] Select[x /. {ToRules[sols]}, Im[Chop[#1]] == 0 & ] --> {-Sqrt[2], Sqrt[2]} Regards, Jean-Marc