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Topic: integration with the symbolic toolbox
Replies: 8   Last Post: May 3, 2012 2:47 PM

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Posts: 10
Registered: 5/3/12
Re: integration with the symbolic toolbox
Posted: May 3, 2012 12:37 PM
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> Try telling Symbolic Math Toolbox about any assumptions you're making about
> the symbolic variables. In particular:
> syms x m
> syms p positive

> > int(exp(-p*x^2),0,inf)
> > For which, I should get the answer :
> > 1/2*sqrt(pi/p)

Thanks a lot!! Just what I was looking for. This does not seem to be documented in the help section. If it is, I have missed it.
With this addition, I get the answer I want.
Otherwise, I accept freely that my previous posts had some stupid omissions.
syms m positive
syms p positive
> f=exp(-m/x^2-p*x^2)
> integ=int(f,0,inf)

But the above trick does not seem to work here. I suppose that, here, the limitations of the symbolic toolbox kick in. Right? Or, is it still possible to add more information to get at the solution?

> So, try to perpetuate the expansion point a litle away from zero
> EDU>> taylor(exp(-m/x^2-p*x^2),x, 'ExpansionPoint',0.01,'Order',6)
> ans =
> exp(- 10000*m - p/10000) - exp(- 10000*m - p/10000)*(x - 1/100)^3*((300000000*m +
> etc...

The above does not work for me. But the following command works fine :

This version is documented in the help. But the one with 'ExpansionPoint' and 'Order' is not (at least, not in R2009b). This is a minor point, but I would just like to make sure that I am looking at the right places in the documentation.

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