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Re: max. value in a plot?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97513] Re: [mg97422] max. value in a plot?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 14 Mar 2009 05:42:43 -0500 (EST)
  • Reply-to: hanlonr at cox.net

expr = (6*15*(10^-6))/((x - 0)^2 + (y - 0)^2 + (0 - 0.005)^2);

Plot3D[expr, {x, -0.05, 0.05}, {y, -0.05, 0.05}]

The image is clipped by the default PlotRange so you cannot see the maximum

Plot3D[expr, {x, -0.05, 0.05}, {y, -0.05, 0.05}, PlotRange -> All]

Maximize[expr, {x, y}]

NMaximize::cvdiv: Failed to converge to a solution. The function may be unbounded. >>

{3.6, {x -> -2.22108555912549*^-16, 
     y -> -1.4320914417659524*^-16}}

expr2 = Rationalize[expr];

Maximize[expr2, {x, y}]

{18/5,{x->0,y->0}}

The min value is out at plus or minus infinity for x and/or y 

Minimize[expr2, {x, y}]

Minimize::natt: The minimum is not attained at any point satisfying the given constraints. >>

{0,{x->Indeterminate,y->Indeterminate}}


Bob Hanlon

---- Oliver <sch_oliver2000 at yahoo.de> wrote: 

=============
Hallo,
i have 2 small questions. how can i find the max. Value of the following Plot?

Plot3D[
(6*15*(10^-6))/((x - 0)^2 + (y - 0)^2 + (0 - 0.005)^2),
 
 {x, -0.05, 0.05}, {y, -0.05, 0.05}]

and how can i plot the range ONLY from the min to the max value?
thanks in Advance



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