##DESCRIPTION
## Algebra: Analytic Trigonometry
##ENDDESCRIPTION

##KEYWORDS('algebra', 'analytic trigonometry', 'addition and subtraction formulas')
 
## tcao , PAID on 11-24-2003

## DBsubject('Trigonometry')
## DBchapter('Analytic Trigonometry')
## DBsection('Addition and Subtraction Formulas')
## Date('6/3/2002')
## Author('')
## Institution('')
## TitleText1('Precalculus')
## EditionText1('3')
## AuthorText1('Stewart, Redlin, Watson')
## Section1('7.2')
## Problem1('8')
DOCUMENT();        # This should be the first executable line in the problem.

loadMacros(
"PG.pl",
"PGbasicmacros.pl",
"PGchoicemacros.pl",
"PGanswermacros.pl",
"PGauxiliaryFunctions.pl"
);

TEXT(beginproblem());
$showPartialCorrectAnswers = 0;


TEXT(EV2(<<EOT));
Use an addition or subtraction formula to write the expression as a 
trigonometric function of one number:
$BR
\(\cos \frac{3\pi}{7} \cos \frac{2\pi}{21} 
+ \sin \frac{3\pi}{7} \sin \frac{2\pi}{21} =\cos \frac{\pi}{A}
=\frac{B}{2} \). 
$BR
\(A=\) \{ans_rule(10)\},
$BR
\(B=\) \{ans_rule(10)\}.
$BR
EOT

$ans1=3;
$ans2=1;

ANS(num_cmp($ans1));
ANS(num_cmp($ans2));

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