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Re: Change integral variables

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88213] Re: Change integral variables
  • From: dh <dh at metrohm.ch>
  • Date: Mon, 28 Apr 2008 04:40:51 -0400 (EDT)
  • References: <fv1fep$es1$1@smc.vnet.net>


Hi,

to prevent evaluation, there is Hold or HoldForm.

To change variable of integration without evaluating the integral, we 

may use Hold or HoldForm which prints nicer.

Hold[Integrate[Sin[Sqrt[x]],x]] 

/.Hold[Integrate[body_,var_]]:>(Hold[Integrate[body1,var]]/.{body1->2 

body /.x->t^2,var->t})

note that we take care of dx=2 dt by writing body1-> 2 body. Note also 

that the first Rule must be delayed.

hope this helps, Daniel





Budaoy wrote:

> In Mathematica, how can I change integral variables? For example in

> integration:

> 

> Integrate[Sin[Sqrt[x]], x] if I want to use t^2=x to instead x in the

> integral, how can I achieve this?

> 

> PS: Does Mathematica have a inertial form of some symbolic command,

> for instance, the above integration, if I only want an integration

> form but not an answer, what can I do?

> 

> Thanks.

> 




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