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Re: What's in an expression?

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  • Subject: [mg132417] Re: What's in an expression?
  • From: Bob Hanlon <hanlonr357 at>
  • Date: Tue, 11 Mar 2014 03:36:08 -0400 (EDT)
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Assuming that answers are entered as strings; to exclude derivatives but
allow other alternative forms:

verifySolution[proposed_, actual_, cond_: {}] :=
 StringFreeQ[proposed, {"Derivative", "'", "D["}] &&
  Simplify[ToExpression[proposed] == actual, cond]

answers = {"Sin'[x]", "Derivative[1][Sin][x]",
   "D[Sin[x],x]", "Cos[x]", "Sin[x]/Tan[x]"};

ToExpression /@ answers // Union


verifySolution[#, Cos[x]] & /@ answers

{False, False, False, True, True}

If the answer must be literally the same as the intended answer:

verifySolution2[proposed_, actual_] :=
 SameQ @@ (StringTrim /@ {proposed, actual})

verifySolution2[#, "Cos[x]"] & /@ answers

{False, False, False, True, False}

Bob Hanlon

On Mon, Mar 10, 2014 at 4:38 AM, <sam.takoy at> wrote:

> Hi all,
> I'm building a little Mathematica system that checks answers entered by
> students. Suppose the question is "what is Sin'[x]?" ad the student
> responds: Sin'[x] which is "correct", but not the intended answer (Cos[x]).
> I'm wondering if there is a general way to approach this sort of problem.
> In particular, is there a way to find out whether a given expression
> includes certain elements (like Derivative)?
> Thank you in advance,
> Sam

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