We are seeing problems with the problem /maCalcDB/setDerivatives7Log/mec8.pg (code copied in below), and I can't see how to fix it although it is a very simple problem.

The seed 1420 gives an example of the problem we're seeing. The student does give a correct answer, but it is not counted correct and gives the message "Can't generate enough points for comparison."

Any ideas? I've run it with diagnostics on, but the output wasn't helpful (to me).

Thanks,

Jason

` ##DESCRIPTION ##KEYWORDS('derivatives', 'logarithmic functions') `

## tcao tagged and PAID on 12-12-2003

## DBsubject('Calculus')

## DBchapter('Differentiation')

## DBsection('Derivatives of Logarithmic Functions')

## Date('6/3/2002')

## Author('')

## Institution('')

## TitleText1('Calculus: Early Transcendentals')

## EditionText1('6')

## AuthorText1('Stewart')

## Section1('3.6')

## Problem1('18')

## differentiation of log function b sin(x) + a x^{x}

##ENDDESCRIPTION

DOCUMENT();

# This should be the first executable line in the problem.

loadMacros(

"PGstandard.pl",

"MathObjects.pl");

TEXT(beginproblem());

$showPartialCorrectAnswers = 1;

Context("Numeric");

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

$c = random(2,8,2);

$b = random(1,9,1);

$d = random(1,9,1);

Context()->flags->set(x=>{limits=>[Compute("$d/$c"),Compute("($d/$c)+10")]}); Context()->flags->set(x=>{limits=>[5,10]});

$Funct = Formula("ln(sqrt(($a*x + $b)/($c*x - $d)))")->reduce;

$Deriv1 = $Funct->D; Context()->texStrings;

BEGIN_TEXT

Let \[ f(x) = $Funct \] $PAR \( f'( x ) = \) \{ans_rule(60) \}

END_TEXT

Context()->normalStrings;

ANS($Deriv1->cmp(diagnostics=>1));

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