Looking at the following code (for example):

Context("Numeric");

$f=Formula("2x^3");

$g=$f->D(x)->reduce;

This gives a formula for $g of the form "2*3x^2".

Is there a way to get webwork to simplify this answer (i.e. multiply the two constants together)?

In reply to Danny Glin
Friday, 19 June 2009, 10:29 AM

### Re: Simplifying Derivatives

by Davide Cervone -
The reduction rules are really very simple-minded, and are not a full Computer Algebra System. There is a lot more that could be done with them, but in their current form, the reduction you ask for is not available. Sorry!

Davide

Davide

In reply to Davide Cervone
Wednesday, 23 June 2010, 11:33 PM

### Re: Simplifying Derivatives

by Dick Lane -
If I ask a student to differentiate a function and analyze that derivative function, I would like feedback (after closing date) about the first step to be close to a student's unsimplified result. E.g., for

$p = Formula( "$a ($b x - $c) ($d x - $e)" ) ;

$p1 = $p -> D(x) ;

I would be content if the student saw $p1 displayed as

$a * $b ($d x - $c) + $a ($b x - $c) $d

involving just the Product Rule (and simpler stuff).

On the other hand, if I also asked for identification of critical point(s), then my Solution would include suitable algebra (with simplification of that derivative expression which keeps $a as a factor for other stuff).

I have had my calculus students use a CAS for many (20+) years and I often wish Webwork had a CAS. The several Student packages in Maple (and rewrite rules in Derive & MuMath) show there is pedagogical value in selective inhibiting the power of a CAS. I am not upset with MathObject symbolic reduction rules being simple-minded.

$p = Formula( "$a ($b x - $c) ($d x - $e)" ) ;

$p1 = $p -> D(x) ;

I would be content if the student saw $p1 displayed as

$a * $b ($d x - $c) + $a ($b x - $c) $d

involving just the Product Rule (and simpler stuff).

On the other hand, if I also asked for identification of critical point(s), then my Solution would include suitable algebra (with simplification of that derivative expression which keeps $a as a factor for other stuff).

I have had my calculus students use a CAS for many (20+) years and I often wish Webwork had a CAS. The several Student packages in Maple (and rewrite rules in Derive & MuMath) show there is pedagogical value in selective inhibiting the power of a CAS. I am not upset with MathObject symbolic reduction rules being simple-minded.

In reply to Dick Lane
Thursday, 24 June 2010, 10:54 AM

### Re: Simplifying Derivatives

by Paul Pearson -
Dear Dick,

You can require student answers to be factored:

http://webwork.maa.org/wiki/FactoringAndExpanding

Also, you should be able to use AnswerHints.pl to provide feedback comments to students who have a correct answer that is not fully factored:

http://webwork.maa.org/wiki/AnswerHints

Good luck!

Paul

You can require student answers to be factored:

http://webwork.maa.org/wiki/FactoringAndExpanding

Also, you should be able to use AnswerHints.pl to provide feedback comments to students who have a correct answer that is not fully factored:

http://webwork.maa.org/wiki/AnswerHints

Good luck!

Paul