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Re: How if I want to assume that -------


Integrate[1/(x-y),{x,0,5}]

If[Re[y] >= 5 || Re[y] <= 0 || Im[y] != 0, Log[5 - y] - Log[-y], Integrate[1/(x - 
y), {x, 0, 5}, 
   Assumptions ->  !(Re[y] >= 5 || Re[y] <= 0 || Im[y] != 0)]]

Simplify[%,{x>y,y>5}]

Log[(y - 5)/y]

Integrate[1/(x-y),{x,0,5},Assumptions->{x>y,y>5}]

Log[(y - 5)/y]

Assuming[{x>y,y>5},Integrate[1/(y-x),{x,0,5}]]

Log[y/(y - 5)]


Bob Hanlon

> 
> From: kong dong <dkong at lnm.imech.ac.cn>
To: mathgroup at smc.vnet.net
> Subject: [mg64579] [mg64550] How if I want to assume that -------
> 
> Thank you for your attention,
> 
> Does there exist a 'assume' function in Mathematica?
> For example, I want to assume that
>         { x>y }
> 
> Thank you!
> 
> 


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