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MathGroup Archive 2005

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Re: Hold[] ReleaseHold[] ? or what ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60192] Re: [mg60168] Hold[] ReleaseHold[] ? or what ?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Wed, 7 Sep 2005 04:03:50 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

Turn off the warnings with Off[NIntegrate::inum].  Note that your problem can 
be solved exactly.

int=Integrate[Sin[x+u],{x,1,2}]

2*Sin[1/2]*Sin[u + 3/2]

Off[Solve::ifun];
soln=Sort[Solve[D[int,u]==0,u],(int/.#1)<(int/.#2)&][[1]];

{int/.soln,soln}//Simplify

{-2*Sin[1/2], {u -> (1/2)*(-3 - Pi)}}

%//N

{-0.958851077208406, {u -> -3.0707963267948966}}


Bob Hanlon

> 
> From: "lupos" <lupos at cheerful.com>
To: mathgroup at smc.vnet.net
> Date: 2005/09/05 Mon PM 10:27:25 EDT
> Subject: [mg60192] [mg60168] Hold[] ReleaseHold[] ? or what ?
> 
> hi all,
> 
> why does the following code work as hoped ?
> 
> In[1]
> fn[u_Real] := NIntegrate[Sin[x + u], {x, 1, 2}];
> FindMinimum[fn[u], {u, 0}]
> 
> Out[2]=
> {-0.9588510772084058, {u -> -3.070796346594197}}
> 
> 
> 
> but the next line generates some warnings/errors altough calculating
> correctly.
> how can the situation be fixed in a nice way ?
> maybe some Hold[] / ReleaseHold[] ?
> 
> In[3]:=
> FindMinimum[NIntegrate[Sin[x + u], {x, 1, 2}], {u, 0}]
> 
> Out[3]:=
> NIntegrate::inum : Integrand Sin[u+x] is not numerical at {x} = {1.5`}.
> NIntegrate::inum : Integrand Sin[u+x] is not numerical at {x} = {1.5`}.
> NIntegrate::inum : Integrand Sin[u+x] is not numerical at {x} = {1.5`}.
> {-0.958851077208406, {u -> -3.0707963268148295}}
> 
> 
> thanks for any hints
> robert.
> 
> 


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