[LON-CAPA-users] Extracting the numerical value from a solve()Maxima command

[Seema Ali]

It is a little messy, I'm still in construction/learning phase. =]

<problem>
<script type="loncapa/perl">$base1 = &random(2,9,1);

do{
   $base2 = &random(2,9,1);
}while($base1==$base2);

$a = &random(2,3,1);
$b = &random(4,7,1) * -1;
$c = &random(1,10,1);

$index = &random(1,2,1);
$leftright = &choose($index,'left','right');

if($leftright=='right')
{
  $power1 = "$a x";
  $power2 = "$b x - $c";

  $power1maxima = "$a * x";
  $power2maxima = "$b * x - $c";
}
else
{
  $power1 = "$a x + $c";
  $power2 = "$b x";

  $power1maxima = "$a * x + $c";
  $power2maxima = "$b * x";
}

$equation = "($power1maxima)*log($base1) = ($power2maxima)*log($base2)";

$solution = &cas('maxima',"float(solve(($power1maxima)*log($base1) = ($power2maxima)*log($base2),x))");
#$solution =~ /(-?\d+(?:\.\d+)?)/;
$solution =~ /(-?\d+?(?:\.\d+)?)/;
$answer = $1;</script><startouttext />Solve for <m>$x$</m> to the nearest hundredth where <m eval='on'>$base1^{$power1} = $base2^{$power2}</m>

<m eval='on'>$ $equation $solution answer=$answer .............  ------ $</m><endouttext />
<numericalresponse answer="$answer">
<responseparam name="tol" type="tolerance" description="Numerical Tolerance" default="0.0001" />

    <textline readonly="no" />
    
</numericalresponse>
</problem>



-----Original Message-----
From: lon-capa-users-bounces at mail.lon-capa.org on behalf of Gerd Kortemeyer
Sent: Fri 1/27/2012 4:41 PM
To: Discussion list for LON-CAPA users
Subject: Re: [LON-CAPA-users] Extracting the numerical value from a solve()Maxima command
 
Hi,

Could you please send me the XML source code for your problem?

Thanks,

- Gerd.

On Jan 27, 2012, at 6:14 PM, Seema Ali wrote:

> Hi,
> 
> This was my attempt to get Maxima to solve the following equation:
> $base1^$power1maxima = $base2^$power2maxima
> where $power1maxima and $power2maxima are linear equations and
> $base1 and $base2 are constant values.
> 
> Below is a snippet of part of my code:
> 
> $solution = &cas('maxima',"float(solve(($power1maxima)*log($base1) = ($power2maxima)*log($base2),x))");
> $solution =~ /(-?\d+(?:\.\d+)?)/;
> $answer = $1;
> 
> 
> Here are a couple of examples of some values:
> 
> Example 1:
> An equation it is trying to solve: (2 * x)*log(7) = (-7 * x - 7)*log(9)
> $solution is [x = -.7980624185332027]
> answer=7
> 
> Example 2:
> An equation it is trying to solve: (2x)log(4)=(?5x?8)log(3)
> $solution is [x=?1063303930517583]
> answer=?1063303930517583
> 
> The answer for Example 2 should be -1.063303930517583.  If I double click on the values on the page I get the decimal point, otherwise if I highlight them which is what I did for Example 2, the decimal is missing, which is a separate issue.
> 
> Example 2 also generates this error:
> ERROR: Computer's answer is incorrect ("-1.063303930517583"). It is likely that the tolerance range [-1.06340393051758, -1.06320393051758] needs to be adjusted.
> This error occurred while processing response 1_7 in part 0
> 
> My tolerance range is 5%.
> 
> I think it is my attempt at a regular expression is probably causing this problem.
> 
> How do I extract the numerical value from a solve command in Maxima?
> 
> 
> Thanks.
> 
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> LON-CAPA-users at mail.lon-capa.org
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