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Topic: Is there way to use something like Assuming with the function SIgn?
Replies: 3   Last Post: Nov 24, 2012 2:40 AM

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 Bob Hanlon Posts: 906 Registered: 10/29/11
Re: Is there way to use something like Assuming with the
Posted: Nov 24, 2012 2:40 AM

"Assuming[assum, expr] evaluates expr with assum appended to
\$Assumptions, so that assum is included in the default assumptions
used by functions such as Refine, Simplify, and Integrate."

list = {1, -2, a, 3};

Assuming[a < 0, Simplify[Sign[list]]]

{1, -1, -1, 1}

However, more compactly

Simplify[Sign[list], a < 0]

{1, -1, -1, 1}

Bob Hanlon

On Fri, Nov 23, 2012 at 3:25 AM, Eduardo Mendes <emammendes@hotmail.com> wrote:
> Hello
>
> I was wondering there is something similar to what can be done with Integrate, Reduce and Limit. Something like
>
> list={1,-2,a,3}
>
> Assuming[a<0,Sign[list]]
>
> Mathematica returns {1,-1,Sign[a],1} and I would like to see something like {1,-1,-1,1}. Can that be done?
>
> Many thanks
>
> Ed
>
>

Date Subject Author
11/24/12 Eduardo Mendes
11/24/12 Bob Hanlon