[ww-bugs] Bug 4099: New: Clarification needed for empty answer list

[bugzilla-daemon at webwork.maa.org]

http://bugs.webwork.maa.org/show_bug.cgi?id=4099

           Summary: Clarification needed for empty answer list
           Product: Problem Libraries
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: Library (OPL)
        AssignedTo: gjennings at csudh.edu
        ReportedBy: zullil at lafayette.edu
        Web browser ---
           version:


OpenProblemLibrary/UMN/calculusStewartET/s_14_7_7.pg

Students should be told to enter NONE if no critical points of a given type
exist. Perhaps modify as below.



#DESCRIPTION
##  Calculus: Local extrema of functions of two variables
##ENDDESCRIPTION

## DBsubject(Calculus - multivariable)
## DBchapter(Differentiation of multivariable functions)
## DBsection(Extreme values and optimization)
## Date(04/18/2014)
## Institution(Colby College)
## Author(Justin Sukiennik)
## MLT(maxMinSaddleList)
## MLTleader(1)
## Level(3)
## MO(1)
## TitleText1('Multivariable Calculus')
## AuthorText1('Stewart')
## EditionText1('7')
## Section1('14.7')
## Problem1('7')
## KEYWORDS('calculus', 'partial derivatives', 'functions of two variables',
'critical points', 'local maximum', 'local minimum', 'saddle point')

########################################################################

DOCUMENT();        # This should be the first executable line in the problem.

loadMacros(
  "PGstandard.pl",
  "MathObjects.pl",
  "PGcourse.pl",
  "parserVectorUtils.pl"
);
##############################################################

install_problem_grader(~~&std_problem_grader);

$showPartialCorrectAnswers = 0;

TEXT(beginproblem);

##############################################################

Context("Numeric");
Context()->strings->add(none=>{},EmptySet=>{alias=>"none"});
Context()->variables->add(y =>'Real', z =>'Real');

$a = list_random(1,4,9,16,25,36);

$sa = Compute("sqrt($a)");

Context("Point");

$P1 = Point($sa,$sa,0);
$P2 = Point(-$sa,-$sa,0);

$ans1 = List(None);
$ans2 = List(None);
$ans3 = List($P1,$P2);

##############################################################

Context()->texStrings;
BEGIN_TEXT
Suppose \(f(x,y) = (x-y)($a-xy).\) Answer the following.
$HR
$BBOLD 1. $EBOLD Find the local maxima of \(f.\) $BBOLD List your answers as
points in the form \((a,b,c)\). Enter NONE if no maxima exist.$EBOLD $BR
Answer (separate by commas): \{ans_rule(30)\} $PAR
$BBOLD 2. $EBOLD Find the local minima of \(f.\) $BBOLD List your answers as
points in the form \((a,b,c)\). Enter NONE if no minima exist.$EBOLD $BR
Answer (separate by commas): \{ans_rule(30)\} $PAR
$BBOLD 3. $EBOLD Find the saddle points of \(f.\) $BBOLD List your answers as
points in the form \((a,b,c)\). Enter NONE if no saddle points exist.$EBOLD $BR
Answer (separate by commas): \{ans_rule(30)\} $PAR
$HR
END_TEXT
Context()->normalStrings;

##############################################################

ANS( $ans1->cmp() );
ANS( $ans2->cmp() );
ANS( $ans3->cmp() );

########################################################################

ENDDOCUMENT();        # This should be the last executable line in the problem.

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