[LON-CAPA-users] Extracting the numerical value from a solve()Maxima command
Seema Ali
sali at vsb.bc.ca
Sat Jan 28 11:32:00 EST 2012
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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