       Re: problem to define a complex quantity

• To: mathgroup at smc.vnet.net
• Subject: [mg116873] Re: problem to define a complex quantity
• From: Peter Pein <petsie at dordos.net>
• Date: Thu, 3 Mar 2011 05:56:41 -0500 (EST)
• References: <ikl2sh\$sni\$1@smc.vnet.net>

```Am 02.03.2011 10:33, schrieb tarun dutta:
> i want to use complex variable such as
> c[i_]=a[i]+I*b[i]    ;where 'a' and 'b' are  both real
> then I get
> conj[c[i]] =a[i]-I*b[i]
> by stating
> conj[x_]:=complexexpand[conjugate[x]];
>
>
> but now i am writing
> c[i_][t_]=a[i][t]+I*b[i][t]
> but i am not getting
> conj[c[i][t]]=a[i][t]-I*b[i][t]
> by stating
> conj[x_]:=ComplexExpand[Conjugate[x]]
>
> moreover am using mathematica version-7
>
> is there any way of writing this thing?
> give some valuable insight.
> regards,
> tarun
>

Hi,

there seems to be a bug in version 7. Everything not contained in the
second argument shoulb be considered real, but this is not the case. So

In:= c[i_][t_]=a[i][t]+I*b[i][t];
conj[x_]:=Simplify[ComplexExpand[Conjugate[x]],Element[Except[_Complex],Reals]];
cc=conj[c[i][t]]
Out= a[i][t]-I b[i][t]

is a workaround.

hth,
Peter

```

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