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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
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"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 <> 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

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