# EquationEvaluators

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## Revision as of 21:42, 14 February 2008

## Equation Answer Evaluation: PG Code Snippet

*This code snippet shows the essential PG code to check student answers that are equations. Note that these are insertions, not a complete PG file. This code will have to be incorporated into the problem file on which you are working.*

PG problem file | Explanation |
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loadMacros("parserImplicitEquation.pl"); |
To check equations given as answers, we don't have to change the tagging and documentation section of the problem file. In the initialization section, we need to include the macros file |

Context("ImplicitEquation"); Context()->variables->set( x=>{limits=>[-2,2]}, y=>{limits=>[0,4]} ); $expr = ImplicitEquation("y = (x-1)^2"); |
In the problem set-up section of the file, we specify that the Context should be
By default, the
Two other notes: if it's possible that a student's solution may evaluate to true for the test points that are used in the answer checker, it may be a good idea to specify what ( $expr = ImplicitEquation("y = (x-1)^2", solutions=>[[0,0],[1,1],[-1,1], [2,4],[-2,4]]);
And, for this type of answer checking it is more likely than for regular formulas that the student will represent the function in a form that exceeds the default problem checking tolerances, and so be marked as incorrect. To correct this, it may be necessary to specify a tolerance; an absolute tolerance can be set in the $expr = ImplicitEquation("y = (x-1)^2", tolerance=>0.0001); |

BEGIN_TEXT Give the equation of a shift of the parabola \(y = x^2\) which is upward opening and has its vertex at (1,0). $PAR equation = \{ ans_rule(35) \} END_TEXT |
The problem text section of the file is as we'd expect. |

ANS( $expr->cmp() ); |
As is the answer. |