Re: Abs help
- To: mathgroup at smc.vnet.net
- Subject: [mg42017] Re: Abs help
- From: "Dr. Wolfgang Hintze" <weh at snafu.de>
- Date: Mon, 16 Jun 2003 03:58:08 -0400 (EDT)
- References: <bc7on7$6bt$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In my opinion, to deal with complex numbers in Mathematica is sometimes
not very intuitive. But if we define our own Abs[]
wehAbs[t_] :=
Sqrt[ComplexExpand[t, TargetFunctions -> {Abs, Arg}]*
ComplexExpand[Conjugate[t], TargetFunctions -> {Abs, Arg}]] //
TrigExpand // Simplify
then
In[1]:=
y = Exp[I*x] + 1;
gives
In[23]:=
wehAbs[y]
Out[23]=
Sqrt[2]*Sqrt[1 + Cos[x]]
Notice that the result differs from yours.
Wolfgang
Rex_chaos wrote:
> hi all,
> Here is a expr
> y=Exp[I*x]+1;
> where x is REAL. I would like to take the absolute value of y
>
> However, it gives
>
> In[1]:=Abs[ExpToTrig[y]]^2
> Out[1]=Abs[1 + Cos[2 x] + \[ImaginaryI] Sin[2 x]]^2
>
> How can I get the result Sin[2 x]^2 + (1+Cos[2 x])^2 ?
>
> How to tell mathematica x is REAL?
>
> Thanks.
>
>