I have a weird issue. This problem is giving an error of 'operator name not defined' when one enters the answer using arccot(x). It has no issues with acot(x), or with cot^-1(x), but for some reason it isn't accepting the arccot(x). Any advice?

Working code is:

DOCUMENT();

loadMacros(

"PGstandard.pl",

"MathObjects.pl",

"AnswerFormatHelp.pl",

"PGML.pl",

"PGcourse.pl",

"contextFraction.pl",

"parserFormulaUpToConstant.pl"

);

TEXT(beginproblem());

$showPartialCorrectAnswers = 1;

$a = random(0,5,1);

$b = random(5,10,1);

$c = random(2,9,1);

Context("Numeric");

Parser::Number::NoDecimals();

$ans = Compute("(1/$c)*(arctan $b - arctan $a)")-> reduce;

BEGIN_PGML

Evaluate the following definite integral.

Your answer must be exact.

[`` \displaystyle \int_{[$a]}^{[$b]} \frac{1}{[$c]+[$c] x^2} \, dx =``][______________________________________]{$ans} [@ AnswerFormatHelp("numbers") @]*

END_PGML

ENDDOCUMENT();

Picture of error is attached.