Re: minimize with complex numbers
- To: mathgroup at smc.vnet.net
- Subject: [mg91258] Re: minimize with complex numbers
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Tue, 12 Aug 2008 04:45:52 -0400 (EDT)
On 8/11/08 at 6:08 AM, shammashahbaz at yahoo.com (shama shahbaz) wrote: >hi , when i use minimize command with real numbers i get the >required answer but with complex number it doesnt give me any answer or er= ror >Syntax::sntxb : Expression cannot begin with "(1+1 i) ` x+(1-1 i) >` x". Syntax::tsntxi : "(1+1 i) ` x" is incomplete; more input >is needed. Syntax::sntxi : Incomplete expression; more input is >needed. >My minimize expression is >((1+1i)*x +(1-1i)*x )^2 +(x+x)^2 You have syntax issues here. In Mathematica, x is the function x to be evaluated at 2. I doubt this is what you had in mind. Also, the symbol i is not defined. You want the built-in symbol I which is the square root of minus 1. However, fixing the syntax issues will not get you what you want. Minimize only works with real valued expressions. If I fix your syntax problems by substituting x for x, y for x and I for i then Expand, I get In:= ((1 + I)*x + (1 - I)*y)^2 + (x + y)^2 // Expand Out= (1 + 2 I) x^2 + 6 y x + (1 - 2 I) y^2 which is clearly only real valued for the case where x^2 == y^2. Minimize is restricted to real valued functions since for complex variables x, y x > y is not defined.