Re: Understanding the Output
- To: mathgroup at smc.vnet.net
- Subject: [mg32818] Re: Understanding the Output
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Thu, 14 Feb 2002 01:43:36 -0500 (EST)
- References: <a4au3v$bs9$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Steven.
For your second example the answer is actually - 1/24(1-x^4)^6.
Subtracting this from the answer given by Mathematica and expanding, we get
Integrate[x^3 (1-x^4)^5,x] - (-1/24(1-x^4)^6)//Expand
1/24
Which is OK - primitives are determined only up to an added constant.
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
"Steven Spear" <smitsky at mindspring.com> wrote in message
news:a4au3v$bs9$1 at smc.vnet.net...
> Hi. I'm having trouble understanding some output in Mathematica. If I
enter
> Int [x-1] dx, the output I receive is ((-2/3) + (2x/3)) Sqrt(-1+x). If I
do
> the calculation by hand, I get 2/3.(x-1)^3/2. If I perform:
> FullSimplify(((-2/3) + (2x/3)) Sqrt(-1+x)), I get the same answer
> (2/3.(x-1)^3/2).
>
> With trying to use u-substitution, and figuring more complex Integrals, it
> get harder to discern the output. For instance: I tried to evaluate the
> Integral Int [x^3 (1-x^4)^5] dx. I may not be correct, but by hand I got
> 1/24.(1-x^4)^6. Mathematica gave a very different output, and using
> FullSimplify didn't seem to help.
>
> Is there any way to get Mathematica to output these values a little
> differently? Am I incorrect on the second example? Any ideas will be
> appreciated. Thanks, Steve
>
>
>