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

*To*: mathgroup at smc.vnet.net*Subject*: [mg55135] Re: [mg55132] How to use "Solve" to get only real number solutions?*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Mon, 14 Mar 2005 03:43:35 -0500 (EST)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

intensity[x_] := 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); Off[Solve::ifun]; Select[Chop[Solve[ intensity[x] == 0.3*(1/4+32/(9*Pi^2)+ (4*Sqrt[2])/(3*Pi)),x]], FreeQ[x/.#,Complex]&] {{x -> -47.4207},{x -> 47.4207}} Bob Hanlon > > From: "PengYu.UT at gmail.com" <PengYu.UT at gmail.com> To: mathgroup at smc.vnet.net > Date: 2005/03/13 Sun AM 04:57:54 EST > To: mathgroup at smc.vnet.net > Subject: [mg55135] [mg55132] How to use "Solve" to get only real number solutions? > > 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] > >