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Re: Re: A simpl(e)ification

  • To: mathgroup at smc.vnet.net
  • Subject: [mg105788] Re: [mg105779] Re: A simpl(e)ification
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 19 Dec 2009 06:25:12 -0500 (EST)
  • Reply-to: hanlonr at cox.net

Simplify[Im[E^(-2 I a) b],
 Element[{a, b}, Reals]]

(-b)*Sin[2*a]

In the second case, also specify that b is not zero

Simplify[Im[E^(-2 I a) 1/b],
 Element[{a, b}, Reals] && b != 0]

-(Sin[2*a]/b)


Bob Hanlon

---- DC <b.gatessucks at gmail.com> wrote: 

=============
You might try

In[3]:= ComplexExpand[Im[E^(-2 I a) 1/b], TargetFunctions -> {Re, Im}]

Out[3]= -(Sin[2 a]/b)

-Francesco

On 12/17/2009 12:22 PM, Pianiel wrote:
> Dear All,
>
> With Mathematica 7.0.1, the following expression;
>
> Simplify[  Im[E^(-2 I a) b],  Assumptions ->  Element[a, Reals]&&
> Element[b, Reals]]
>
> gives
>
> -b Sin[2 a]
>
> But:
>
> Simplify[  Im[E^(-2 I a) 1/b],  Assumptions ->  Element[a, Reals]&&
> Element[b, Reals]]
>
> gives
>
> Im[E^(-2 I a)/b]
>
> So we see that the Im[] is not simplified. Why?
>
> Any idea how to help mathematica to handle the simplification shown in
> the second example. It seems to be so similar to the first kind...
>
> Thanks in advance
>
> Pianiel
>


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