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MathGroup Archive 2002

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RE: How can solue the inequation system in mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34758] RE: [mg34728] How can solue the inequation system in mathematica
  • From: "DrBob" <majort at cox-internet.com>
  • Date: Wed, 5 Jun 2002 03:38:16 -0400 (EDT)
  • Reply-to: <drbob at bigfoot.com>
  • Sender: owner-wri-mathgroup at wolfram.com

Here's a little code and a plot to get you started:

Needs["Graphics`InequalityGraphics`"]
ineq = {2*x^3 + y^ +1 > 0,
      5*x^2 - y^2 + 5 < 0};
eqns = {x, y /. #} & /@ 
    Flatten[Solve[#, y] & /@ (ineq /. {Greater -> Equal, Less ->
Equal})]
xRange = {x, -10, 10};
yRange = {y, -20, 20};
Show[{
    ParametricPlot[Evaluate[eqns], Evaluate[xRange], 
      DisplayFunction -> Identity],
    InequalityPlot[ineq, Evaluate[xRange], Evaluate[yRange], 
      DisplayFunction -> Identity]},
  PlotRange -> {Rest[xRange], Rest[yRange]},
  ImageSize -> 400,
  DisplayFunction -> $DisplayFunction]

One issue you face is "What does a solution look like?"  A picture?  A
dichotomy of the solution set?  If the latter, you can find
intersections of the equality curves and, based on those, state the
solution set in y for each range of x values (or in x for each range of
y values).

Bobby Treat

-----Original Message-----
From: DrBob [mailto:majort at cox-internet.com] 
To: mathgroup at smc.vnet.net
Subject: [mg34758] RE: [mg34728] How can solue the inequation system in
mathematica

Check out the InequalityGraphics package (Addons>Standard
Packages>Graphics>InequalityGraphics in Help), and you can also try
InequalityInstance in the Developer package.

I think you'll have to figure it out yourself, with Mathematica's help.
For instance, in the problem you've listed below, you can fix x and
solve the corresponding equations for y, and figure out from that what
range of y values are feasible for that x.  You can do the similar thing
fixing x and solving for y.  You might even make it fairly automatic, as
InequalityGraphics has done.

Bobby

-----Original Message-----
From: MailPhys [mailto:physics.nsu at bdvn.vnd.net] 
To: mathgroup at smc.vnet.net
Subject: [mg34758] [mg34728] How can solue the inequation system in mathematica


Dear friends
This my question. How can I solve the Inequation system in mathematica.
I haven't seen any command for that
for example
2*x^3 +y^ +1 >0
5*x^2 -y^2+5<0

If you  know that , please point out to me
Thank you






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