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Re: Difficulties with Re

  • To: mathgroup at smc.vnet.net
  • Subject: [mg98353] Re: Difficulties with Re
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Wed, 8 Apr 2009 02:48:12 -0400 (EDT)
  • References: <grcgjq$pmv$1@smc.vnet.net>

Hi Aaron,

You could argue that it "works"in the second example as well. What
would you think Simplify should do? Look at TreeForm[Re[Exp[(x + I y)
^2]] ] and TreeForm[E^(x^2 - y^2) Cos[2 x y]] . The latter (which you
would consider the Simplified version) contains 17 boxes, whereas the
former (Mathematica's output) contains only 12. Ergo, your desired
result is not the most simple representation and Mathematica is right
not to simplify it that way.

You can force Mathematica to do it your way: Assuming[x > 0 && y > 0,
Re[E^Expand[(x + I y)^2]] // Simplify]

Cheers -- Sjoerd


On Apr 6, 11:04 am, Aaron Fude <aaronf... at gmail.com> wrote:
> Hi,
>
> Of the following two expressions, the first "works", while the second
> doesn't. How does one make it work?
>
> Assuming[x > 0 && y > 0, Re[Exp[x + I y]] // Simplify]
> Assuming[x > 0 && y > 0, Re[Exp[(x + I y)^2]] // Simplify]
>
> Many thanks in advance,
>
> Aaron



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