Re: How to use "Solve" to get only real number solutions?

*To*: mathgroup at smc.vnet.net*Subject*: [mg55140] Re: [mg55132] How to use "Solve" to get only real number solutions?*From*: "Christoph Lhotka" <lhotka at astro.univie.ac.at>*Date*: Mon, 14 Mar 2005 03:43:39 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi there is a package, which redefines all functions, so that you only get real valued solutions called RealOnly You load it into your Mathematica Session with In[..]:=Needs["Miscellaneous`RealOnly`"] Now you will get only real answers... Another option is to use the function Select... In[..]:=Solve[...] Out[...]:={x->,x->,...} In[..]:=Select[%,FreeQ[#[[2]], I * _]&] Out[..]:=... Or use DeleteCases to delete all expression holding imaginary parts. best wishes... On Sun, 13 Mar 2005 04:57:54 -0500 (EST) "PengYu.UT at gmail.com" <PengYu.UT at gmail.com> wrote: > Hi All > > For example I have the following function and I want to find the > solution of the quation shown below. But Mathematica showns not only > real number solutions. Do you know how to restrict the solutions to > only real numbers. Thanks! > > Best wishes, > Peng > > intensity[x_, Î´_, p_, Î»_] := 1/4 + (2*Cos[(Pi*x)/100])/Pi + > (4*Cos[(Pi*x)/100]^2)/Pi^2 - (2*Cos[(3*Pi*x)/100])/(3*Pi) - > (8*Cos[(Pi*x)/100]*Cos[(3*Pi*x)/100])/(3*Pi^2) + > (4*Cos[(3*Pi*x)/100]^2)/(9*Pi^2) > > Solve[intensity[x, 0, 200, 50] == 0.3*(1/4 + 32/(9*Pi^2) + > (4*Sqrt[2])/(3*Pi)), x] > -- Christoph Lhotka -- University of Vienna Institute for Astronomy Tuerkenschanzstr. 17 1180 Vienna, Austria fon. +43.1.4277.518.41 mail. lhotka at astro.univie.ac.at