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Danny

I fear that my main problem is a lack of understanding of basic things involving MathObjects. I was hoping to compute answers and wrong answers using things like $F><$G and $F.$G where $F and $G are Vector functions. But they don't seem to work for me. Using your suggestion to move Context()->texStrings; to before the $mc definition I am now okay but don't understand why I can't display things like $F><$G.

I'm reluctant to post an example due to making public my poor programming skills -- but I will go ahead and post an example that does not work for me and hopefully gain some insight into what is wrong with my thinking. I expect it has to do with executing and displaying things like $F><$G and $F.$G.

Also, concerning my thought of finding an alternative to using Multiple Choice, I wish I could have a little more control over the display of the multiple choice questions. For example, I would like to have more space between the rows and so on.

Thanks to all who have responded to my post.

David Gilliam

%%%%%%%%%%%%%%%%%%%%%%%%

DOCUMENT();

loadMacros(

"PGstandard.pl",

"PGML.pl",

"PGgraphmacros.pl",

"MathObjects.pl",

"PGcourse.pl",

"PGchoicemacros.pl",

"PGbasicmacros.pl",

);

TEXT(beginproblem());

$showPartialCorrectAnswers = 1;

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

Context("Vector");

$context = Context();

$context->flags->set(ijk=>1);

$context->variables->add( t=>'Real');

$a= random(2,5,1);

$b= random(2,4,1);

while ($a == $b)

{$b = non_zero_random(2,4,1); }

$a1 = non_zero_random(2,4,1);

$a2 = non_zero_random(-3,3,1);

$a3 = non_zero_random(-1,1,1);

do { $a3 = non_zero_random(-1,1,1); } until ($a3 != $a1 || $a3 != $a2);

$b1 = non_zero_random(-3,3,1);

$b2 = random(-1,1,1);

$b3 = non_zero_random(-5,5,1);

do { $b3 = non_zero_random(-5,5,1); } until ($a1 * $b1 + $a2 * $b2 + $a3 * $b3 != $a1*$b3 + $a2*$b2 + $a3*$b1);

$n= random(1,4,1);

$m= random(1,6,1);

$f1= Formula( "$a1 t^$n" )->reduce ;

$f2= Formula(" $a2 sin($a t) ")->reduce ;

$f3= Formula(" $a3 " )->reduce;

$F = Compute( "< $f1 , $f2, $f3>" ) ;

$g1= Formula(" $b1 cos($b t)")->reduce ;

$g2= Formula(" $b2 ")->reduce ;

$g3= Formula( "$b3 e^{$m t}")->reduce ;

$G = Compute("< $g1 , $g2, $g3>" );

# Rather than computing FxG by hand like this (which does work well)

$FxG = Compute(" <$a3 $b3 e^{$m t} - $a3 $b2 , -($a1 $b3 t^$n e^{$m t} - $a3 $b1 cos($b t)), $a1 $b2 t^{$n} - $a2 $b1 sin($a t) cos($b t)> ")->reduce;

# I had hoped to simply compute

$FprodG = Formula("$F >< $G")->reduce;

# and then compute extra wrong answers using things like

$GprodF = Compute("$G >< $F");

$FdotG = Compute("$F . $G");

Context()->texStrings;

$mc = new_checkbox_multiple_choice();

$mc -> qa (" "," \($FprodG\) ");

$mc -> extra( " \($GprodF \) ", "\($FdotG \) " );

$mc -> makeLast("None of the above");

BEGIN_PGML

Let [` \mathbf{F}(t) = \displaystyle [$F] `] and [` \mathbf{G}(t) = \displaystyle [$G] `] and find [` \mathbf{F}(t) \times \mathbf{G}(t) `].

[@ $mc -> print_q() @]***

[@ $mc -> print_a() @]***

END_PGML

Context()->normalStrings;

$showPartialCorrectAnswers = 1;

ANS( checkbox_cmp( $mc->correct_ans() ) );

COMMENT('PGML version');

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

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

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