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Re: SetDelayed and NIntegrate

  • To: mathgroup at
  • Subject: [mg47831] Re: [mg47805] SetDelayed and NIntegrate
  • From: Anton Antonov <antonov at>
  • Date: Thu, 29 Apr 2004 00:33:49 -0400 (EDT)
  • References: <>
  • Sender: owner-wri-mathgroup at

Mukhtar Bekkali wrote:

>Very simple question.   Is it possible in Mathematica 5 to execute this
>f[x_,y_]:=f[x,y]  (*where f[x,y] is some known function*)
>I get a message that Integrand is not numeric and FindRoot stops.   I would
>like to make clear that I do not want to use Integrate.
>My other question is why this code does not work
>Thanks. Mukhtar Bekkali
With this lines you are trying to find a symbolic derivative of the 
result of a numerical function (which is a number):


May be you want NIntegrate[D[f[x,y],x],{y,0,1}] ?

In this case you can try this:

Clear[f, g, h, x, y]

f[x_, y_] := (x - 0.5)^2*y^2
g[(x_)?NumericQ] := NIntegrate[D[f[x1, y], x1] /. x1 -> x, {y, 0, 1}]
FindRoot[g[x] == 0, {x, 1}]

{x -> 0.5}

Anton Antonov
Wolfram Research, Inc.

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