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<h2>Domain and Range of a Function</h2>

[[File:DomainRange1.png|300px|thumb|right|Click to enlarge]]
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This PG code shows how to evaluate answers that are inequalities which use different variables.
</p>
* File location in OPL: [https://github.com/openwebwork/webwork-open-problem-library/blob/master/OpenProblemLibrary/FortLewis/Authoring/Templates/Precalc/DomainRange1.pg FortLewis/Authoring/Templates/Precalc/DomainRange1.pg]
* PGML location in OPL: [https://github.com/openwebwork/webwork-open-problem-library/blob/master/OpenProblemLibrary/FortLewis/Authoring/Templates/Precalc/DomainRange1_PGML.pg FortLewis/Authoring/Templates/Precalc/DomainRange1_PGML.pg]

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<th> PG problem file </th>
<th> Explanation </th>
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[http://webwork.maa.org/wiki/Tagging_Problems Problem tagging data]
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<p>
<b>Problem tagging:</b>
</p>
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<!-- Initialization section -->

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<pre>
DOCUMENT();

loadMacros(
"PGstandard.pl",
"MathObjects.pl",
"contextInequalities.pl",
"AnswerFormatHelp.pl",
);

TEXT(beginproblem());
</pre>
</td>
<td style="background-color:#ddffdd;padding:7px;">
<p>
<b>Initialization:</b>
We must load <code>contextInequalities.pl</code>.
</p>
</td>
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<!-- Setup section -->

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<pre>
Context("Numeric");

$f = Compute("sqrt(x-4)");

Context("Inequalities-Only")->variables->are(x=>"Real");
Context()->flags->set(formatStudentAnswer=>'parsed');

$domain = Compute("x >= 4");
</pre>
</td>
<td style="background-color:#ffffcc;padding:7px;">
<p>
<b>Setup 1:</b> 
We specify the context in a way that requires students to enter their answer using inequalities and the variable x.  If we had used <code>Context("Inequalities")</code> instead, then students would also be able to enter answers using interval notation.  For more details, please see [http://webwork.maa.org/pod/pg_TRUNK/macros/contextInequalities.pl.html contextInequalities.pl.html]
</p>
<p>
We use <code>formatStudentAnswer=>'parsed'</code> and <code>Compute()</code> so that the student's answer are left as fractions rather than reduced to decimals.
</p>
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<!-- Main text section -->

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<td style="background-color:#ffdddd;border:black 1px dashed;">
<pre>
Context()->texStrings;
BEGIN_TEXT
Suppose \( f(x) = $f \).  Enter inequalities for the 
domain and range of \( f \).
$BR
$BR
Domain: 
\{ ans_rule(20) \}
\{ AnswerFormatHelp("inequalities") \}
$BR
END_TEXT
Context()->normalStrings;
</pre>
<td style="background-color:#ffcccc;padding:7px;">
<p>
<b>Main Text 1:</b>
</p>
</td>
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<!-- Answer evaluation section -->

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<pre>
$showPartialCorrectAnswers = 1;

ANS( $domain->cmp() );
</pre>
<td style="background-color:#eeccff;padding:7px;">
<p>
<b>Answer Evaluation 1:</b>
</p>
</td>
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<pre>
Context("Inequalities-Only")->variables->are(y=>"Real");
Context()->flags->set(formatStudentAnswer=>'parsed');

$range  = Compute("y >= 0");
</pre>
</td>
<td style="background-color:#ffffcc;padding:7px;">
<p>
<b>Setup 2:</b> 
We must reset the context and the variable so that students must enter the variable y in their answer.
</p>
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<!-- Main text section -->

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<td style="background-color:#ffdddd;border:black 1px dashed;">
<pre>
Context()->texStrings;
BEGIN_TEXT
Range:$SPACE$SPACE
\{ ans_rule(20) \}
\{ AnswerFormatHelp("inequalities") \}
END_TEXT
Context()->normalStrings;
</pre>
<td style="background-color:#ffcccc;padding:7px;">
<p>
<b>Main Text 2:</b>
</p>
</td>
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<!-- Answer evaluation section -->

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<pre>
ANS( $range ->cmp() );
</pre>
<td style="background-color:#eeccff;padding:7px;">
<p>
<b>Answer Evaluation 2:</b>
</p>
</td>
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<!-- Solution section -->

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<pre>
Context()->texStrings;
BEGIN_SOLUTION
${PAR}SOLUTION:${PAR}
Solution explanation goes here.
END_SOLUTION
Context()->normalStrings;

COMMENT('MathObject version.');

ENDDOCUMENT();
</pre>
<td style="background-color:#ddddff;padding:7px;">
<p>
<b>Solution:</b>
</p>
</td>
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