Update with math objects

Author: gajennings

OpenProblemLibrary/Utah/Calculus_II/set14_Differential_Equations/set14_pr6.pg

@@ -6,6 +6,7 @@
 ## Institution(Univeristy of Utah)
 ## Author(Utah ww group)
 ## Level(5)
+## MO(1)
 ## Static(1)
 ## TitleText1('Calculus')
 ## AuthorText1('Dale Varberg, Edwin J. Purcell, and Steve E. Rigdon')
@@ -18,46 +19,46 @@ DOCUMENT();        # This should be the first executable line in the problem.
 
 loadMacros(
   "PGstandard.pl",
-  "PGchoicemacros.pl",
+  "MathObjects.pl",
   "PGcourse.pl"
 );
 
 TEXT( beginproblem() ); 
 
 $showPartialCorrectAnswers = 1;
 
-$pi = 3.141592654;
-$ans1 = "(1/12)*cos(40*sqrt(2)*t)";
-$ans2 = 1;
-$ans3 = 2*$pi/40/sqrt(2);
+Context("Numeric");
+Context()->variables->are(t=>'Real');
 
+
+$ans1 = Compute("(1/12)*cos(40*sqrt(2)*t)");
+$ans2 = Real(1);
+$ans3 = Compute("2*pi/(40*sqrt(2))");
+
+Context()->texStrings;
 BEGIN_TEXT
 
 A spring with a spring constant \(k\) of 100 pounds per foot
 is loaded with 1-pound weight and brought to equilibrium.  It
 is then stretched an additional 1 inch and released.  Find
 the equation of motion, the amplitude, and the period.  Neglect
-friction.  Then
-
-$BR
-$BR
+friction.  
 
+$PAR
+The displacement \(y\), in feet from equilibrium is 
 \( y(t) = \) \{ans_rule(80)\} $BR
-where \(t\) is time in (seconds) and \(y(t)\) is displacement (in feet).
-$BR
-$BR
+where \(t\) is time in seconds since the spring was released, and the initial 1 in. stretch is regarded as a positive displacement.
+$PAR
 
 Amplitude: \{ans_rule(15)\} inch(es) $BR
 
 Period:  \{ans_rule(15)\} second(s).
 
 END_TEXT
+Context()->normalStrings;
 
-#Answer: \( y(x) = C_{1} \) \{NAME_ANS_RULE(second_answer,25)\} \( + C_{2} \) \{NAMED_ANS_RULE(answer_rule,25)\}.
-
-
-ANS(fun_cmp($ans1, vars=>"t"));
-ANS(num_cmp($ans2));
-ANS(num_cmp($ans3));
+ANS($ans1->cmp());
+ANS($ans2->cmp());
+ANS($ans3->cmp());
 
 ENDDOCUMENT();        # This should be the last executable line in the problem.