## DESCRIPTION
## Trigonometry: periodic answers
## ENDDESCRIPTION

## KEYWORDS('trigonometry', 'periodic answer')

## DBsubject('WeBWorK')
## DBchapter('WeBWorK Tutorial')
## DBsection('Fort Lewis Tutorial 2011')
## Date('01/30/2011')
## Author('Paul Pearson')
## Institution('Fort Lewis College')
## TitleText1('')
## EditionText1('')
## AuthorText1('')
## Section1('')
## Problem1('')


####################################
#  Initialization

DOCUMENT();  

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

TEXT(beginproblem());


####################################
#  Setup

Context("Numeric");

#
#  We redefine the function whose
#  name is tan(x) to take values
#  exp(pi * x).
#
Context()->functions->remove("tan");
package NewFunc;
# this next line makes the function a 
# function from reals to reals
our @ISA = qw(Parser::Function::numeric);
sub tan {
  shift; my $x = shift;
  return CORE::exp($x*3.1415926535);
}
package main;
# Make it work on formulas as well as numbers
sub tan {Parser::Function->call('tan',@_)} 
#  Add the new functions to the Context
Context()->functions->add( 
  tan => {class =>'NewFunc', TeX =>'\tan'}, );



####################################
#  Main Text

Context()->texStrings;
BEGIN_TEXT
Simplify the expression as much as possible.
$BR
$BR
\( \tan(x) \cos(x) \) = \{ ans_rule(20) \}
\{ AnswerFormatHelp("formulas") \}
END_TEXT
Context()->normalStrings;


###################################
#  Answer evaluation

$showPartialCorrectAnswers = 1;

ANS(Formula("sin(x)")->cmp() 
->withPostFilter(AnswerHints(
  Compute("tan(x)*cos(x)") => 
  "No credit for entering what you were given.",
))
);


###################################
#  Solution

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

COMMENT("MathObject version.  Prevents students from entering trivial identities (entering what they were given).  Redefines 'tan(x)' internally as 'exp(pi*x)'.");

ENDDOCUMENT();