       RE: PowerExpand in mathematica

• To: mathgroup at smc.vnet.net
• Subject: [mg31871] RE: [mg31843] PowerExpand in mathematica
• From: "David Park" <djmp at earthlink.net>
• Date: Sat, 8 Dec 2001 05:51:48 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Peter,

I think that the correct answer is 1/t, not -1/t. Nevertheless, this is just
the type of problem that PowerExpand might give the incorrect answer.
PowerExpand is an operation that in general is done at your own risk.

Try a series expansion on the parts of your expression. Or plot your
expression and 1/t. Or try this

Series[(-1/t)^(3/2) Sqrt[-t], {t, 0, 10}]
1/t + O[t]^4

David Park

> From: Peter [mailto:ptrsn2001 at yahoo.com]
To: mathgroup at smc.vnet.net
>
> Hi,
>
> Is this a known bug, feature? Or I am doing something wrong?
> -------------------------------
> Mathematica 4.0 for Linux
> Copyright 1988-1999 Wolfram Research, Inc.
>  -- Motif graphics initialized --
>
> In:= PowerExpand[(-1/t)^(3/2) Sqrt[-t]]
>
>         1
> Out= -
>         t
> ---------------------------------
> The correct answer is -1/t, of course.
>
> Thanks,
> Peter
>

```

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