Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.soft-sys.math.mathematica > #1927

Re: Solve / Reduce isolating results.

Show all headers | View raw

On 4/29/11 at 7:35 AM, lrebanks@netvigator.com (Lea Rebanks) wrote:

>Given the enclosed code - see below. Please could someone help me
>setup the code to Solve / Reduce for these 2 missing values only
>required

>{SQ1 -> 5292, XX -> 0.25}

>(I don't want multiple results.) I want positive numbers & NOT
>Complex..

The simplest way I can think of to do what you want is to select
the result you want from the list of returned results by
specifying the desired properties. That is:

In[14]:= Quiet@
  Cases[NSolve[{(1/6)*((SQ1*196)*2)^3 - (1/
          6)*((((2.75 + XX)*((3.75 + XX)*21^2))*100)*2)^3 ==
      1.2902698935932682*^18, (1/6)*((SQ1*100)*2)^3 - (1/
          6)*((((2.75 + XX)*((3.75 + XX)*21^2))*36)*2)^3 ==
      1.883856772422697*^17}, {SQ1,
     XX}], _?((XX /. #) > 0. && (SQ1 /. #) > 0. &)]


Out[14]= {{SQ1->5292.,XX->0.25}}

Here, I use Quiet to suppress the warning messages Mathematica
generates indicating it really isn't meaningful to compare a
complex value to zero. Since you aren't interested in complex
values, it is safe to ignore or suppress this warning.

Note, I also changed Solve to NSolve since that will get rid of
another warning message and NSolve is  specifically intended for
approximate numeric answers.

Back to comp.soft-sys.math.mathematica | Previous | Next | Find similar | Unroll thread

Thread

Re: Solve / Reduce isolating results. Bill Rowe <readnews@sbcglobal.net> - 2011-04-30 09:52 +0000

csiph-web