[LON-CAPA-users] {Disarmed} RE: Formula response won't recognize "pi"

SIMIN, GRIGORY SIMIN at engr.sc.edu
Thu Nov 21 14:52:08 EST 2019

Many thanks!
I will give it a try!

From: LON-CAPA-users <lon-capa-users-bounces at mail.lon-capa.org> On Behalf Of Justin Gray
Sent: Thursday, November 21, 2019 2:28 PM
To: Discussion list for LON-CAPA users <lon-capa-users at mail.lon-capa.org>
Subject: Re: [LON-CAPA-users] Formula response won't recognize "pi"

You can evaluate the answer using Maxima and allow for a tolerance using mathresponse. In Maxima, the constant pi is written as %pi. Here is a possible coding for this problem, which will accept either %pi or a numerical approximation for pi:

<script type="loncapa/perl">
$function = "1/sqrt(4*(%pi)^2*L*C)";
$answer=&xmlparse('The correct answer is <m eval="on">$\frac{1}{\sqrt{4\cdot\pi^{2} \cdot L\cdot C}}$</m>');

<startouttext />
    <p>Enter <m>$ \frac{1}{\sqrt{4\cdot\pi^{2} \cdot L\cdot C}} $</m></p>
<endouttext />

<mathresponse answerdisplay="$answer" cas="maxima" args="$function">
    <answer>is(abs((RESPONSE[1])/(LONCAPALIST[1]) - 1) < 0.01);</answer>
    <textline readonly="no" size="100" spellcheck="none" />

You will probably want to give students some instruction for formatting their answer.



Justin Gray
Senior Lecturer | Department of Mathematics
Simon Fraser University | SCK 10531
8888 University Dr., Burnaby, B.C. V5A 1S6
T: 778.782.4237


On Thu, Nov 21, 2019 at 11:14 AM H. K. Ng <hkng at fsu.edu<mailto:hkng at fsu.edu>> wrote:

Formularesponse using  cas with maxima works great.

<script type="loncapa/perl">
$ansa  = &cas('maxima','1/sqrt(4*pi^2*L*C)');

<startouttext />What is formula for resonant frequency for an LC circuit? <endouttext /><br />

<startouttext /><m>$ \omega_{res} = $</m><endouttext />
<formularesponse answer="$ansa" id="12">
    <textline readonly="no" />



On Thu, Nov 21, 2019 at 11:05 AM SIMIN, GRIGORY <SIMIN at engr.sc.edu<mailto:SIMIN at engr.sc.edu>> wrote:

Hi all!

I've found a strange issue in some problems requiring formula response.

I have a simple question to enter the formula for the resonant frequency.

An example of correct answer is (in other variations the formula could be a bit more complex than this one)


The correct solution is checked by sampling L and C values.

When I am entering the answer, I can see that LON-CAPA recognizes it because it displays the formatted formula as I am entering it:

[cid:image001.jpg at 01D5A07B.3EF6C940]

But when I press submit, I got the response:

“unable to understand formula”

By experimenting with this, I found that the issue happens because of “pi” being a part of the answer.

If pi is replaced with 3.141, everything would work.

But it feels weird asking students to enter 3.141 instead of pi; besides, I don’t even want to give them a hint that pi is a part of the answer.

Why is this happening? Apparently LON-CAPA knows what “pi” means because it displays it correctly.



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