Re: How to evaluate a NIntegrate expression properly
- To: mathgroup at smc.vnet.net
- Subject: [mg39722] Re: How to evaluate a NIntegrate expression properly
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Mon, 3 Mar 2003 23:49:11 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <b3v6uf$k41$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
f[y_] := Integrate[y^2*x^2, {x, 0, 3}]
NSolve[Evaluate[f[y] == 20], y]
or
f[y_?NumericQ] := NIntegrate[y^2*x^2, {x, 0, 3}]
FindRoot[f[y] == 20, {y, 0, 20}]
Regards
Jens
Yong Xiao wrote:
>
> Hi,
> I have a problem regarding to how to use NIntegrate and NSolve together.
> A sampe is as follwing:
>
> f[y_] := NIntegrate[y^2*x^2, {x, 0, 3}]
> NSolve[f[y] == 20, y]
>
> Complaint:
> \!\(NIntegrate::"inum" \(\(:\)\(\ \)\) "Integrand \!\(2.25` \\\\ y\^2\)
> is
> not numerical at \!\({x}\) = {1.5`}."\)
>
> Thanks in advance.
>
> X.Y.