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From: <HIDDEN>
Newsgroups: comp.soft-sys.matlab
Subject: Re: i can't integrate this function, please help!!!
Date: Sat, 05 May 2012 00:19:41 -0500
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On 5/4/2012 11:39 PM, Roger Stafford wrote:
> "Nasser M. Abbasi"<nma@12000.org>  wrote in message<jo268r$hd0$1@speranza.aioe.org>...
>> write 1/4 and not 0.25 ! This made the code go via
>> a symbolic path internally, much easier on the poor symbolic
>> engine ;)
>>
>> ps. and you got too many extra paranthesis, not needed.
>> And it always better to break down the terms a little, to
>> make it easier on the eyes to see things:
>>
>> -----------------------------
>> clear all
>> syms x Z;
>> den = (1-x)^1/4 * (Z-3*x)^1/4;
>> int( 1 /den ,x)
>> ------------------------------
>>
>> ans =
>>
>> (16*log((Z - 3*x)/(x - 1)))/(Z - 3)
>>
>> --Nasser
> - - - - - - - - - -
>    If you differentiate that indefinite integral, Nasser, you will get this for an answer:
>
>   16/((Z-3*x)*(1-x))
>
> which is equal to
>
>   1/(((1-x)^1)/4*((Z-3*x)^1)/4)
>
>    The symbolic toolbox played a trick on you.  It didn't recognize
>
>   (1-x)^1/4 and (Z-3*x)^1/4
>
> the way you intended.  You need parentheses around the 1/4 in each factor.
>
> Roger Stafford

good point Roger, I removed too many paranthesis.

yes, x^1/4 != x^(1/4)   :)

And I did not bother to differentiate to check the computer
did it right. I should have.

thanks

--Nasser