RE: complex coefficients and rules...
- To: mathgroup at smc.vnet.net
- Subject: [mg28222] RE: [mg28203] complex coefficients and rules...
- From: "David Park" <djmp at earthlink.net>
- Date: Thu, 5 Apr 2001 03:00:35 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Richard, This is one possible method: myConjugate[expr_] := TrigToExp[ComplexExpand[Conjugate[expr]]] Exp[-I y] + Exp[-4 I z] // myConjugate E^(I*y) + E^(4*I*z) ComplexExpand will expand assuming that variables are real. (You can specify which ones are complex.) TrigToExp puts the result back into exponential form, if that is what you want. A second approach is simple to make your "cumbersome" procedure into a less cumbersome routine. myConjugate2[expr_] := expr /. Complex[a_, b_] -> Complex[a, -b] Exp[-I y] + Exp[-4 I z] // myConjugate2 E^(I*y) + E^(4*I*z) David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ > From: Richard Easther [mailto:easther at physics.columbia.edu] To: mathgroup at smc.vnet.net > > Hi, > > I am having some trouble applying some simple rules to complex > expressions. > > For instance, > > Exp[-4 I y] /. I-> -I > > yields > > Exp[-4 I y] > > This seemed a bit odd, so I looked at the "full form" and found, > > Power[E, Times[Complex[0, -4], y]] > > However, trying the match > > Exp[-4 I y] /. a_ I -> -a I > > doesn't work either, since FullForm[a I ] is Times[Complex[0, -1], a] > and so the patterns do not match. > > All I want is a simple complex conjugate (the Conjugate function does > not assume that y is real), that maps I->-I. The more tricky > > Exp[-4 I y] /. Complex[a_ ,b_] -> Complex[a,-b] > > does work, but it is seems a little cumbersome. > > In any case my question is: is there a general way to avoid having to do > this, or is Mathematica always going to assume that any algebraic > constant is potentially complex? > > Richard >