Re: problem with double integral
- To: mathgroup at smc.vnet.net
- Subject: [mg107612] Re: problem with double integral
- From: "Kevin J. McCann" <Kevin.McCann at umbc.edu>
- Date: Fri, 19 Feb 2010 03:36:14 -0500 (EST)
- References: <hlj3vf$rop$1@smc.vnet.net>
You did not specify what a is. In NIntegrate it has to be a numerical
value. Also, the "_?NumberQ" construct prevents NIntegrate from trying
any symbolic tricks and giving errors.
Clear[i, Q]
a = 1.0;
i[Q_?NumberQ] := NIntegrate[Exp[-(a/(4 x)) - 4 x], {x, \[Infinity], Q}]
NIntegrate[1/i[Q], {Q, 0, 1}]
I get -71.477 for this.
Kevin
Regina wrote:
> Hi there,
> i got a problem: how can i evaluate the following integral:
> define:
> i[Q_] := Integrate[(Exp[-a/(4 x) - 4 x]), {x, \[Infinity], Q}]
> now i want to compute:
> NIntegrate[1/i[Q], {Q, 0, 1}]
>
> what am i doing wrong? how can i integrate that function?
>