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1 : jjholt 314 ## DESCRIPTION
2 :     ## Related Rates
3 :     ## ENDDESCRIPTION
4 : jj 213
5 : jjholt 314 ## KEYWORDS('Derivative', 'Related Rates', 'Focal Length')
6 :     ## Tagged by nhamblet
7 :    
8 :     ## DBsubject('Calculus')
9 :     ## DBchapter('Differentiation')
10 :     ## DBsection('Related Rates')
11 :     ## Date('')
12 :     ## Author('')
13 :     ## Institution('OSU')
14 :     ## TitleText1('')
15 :     ## EditionText1('')
16 :     ## AuthorText1('')
17 :     ## Section1('')
18 :     ## Problem1('')
19 :    
20 : jj 213 DOCUMENT(); # This should be the first executable line in the problem.
21 :    
22 :     loadMacros("PG.pl",
23 :     "PGbasicmacros.pl",
24 :     "PGchoicemacros.pl",
25 :     "PGanswermacros.pl",
26 :     "PGauxiliaryFunctions.pl");
27 :    
28 : gage 269 TEXT(beginproblem());
29 : jj 213 $showPartialCorrectAnswers = 1;
30 :    
31 :     undef($q);
32 :    
33 :     $f = random(1,8,1);
34 :     while (not defined($q) or $q == $f) {$q=random(1,8,1)};
35 :    
36 :     # Present the text.
37 :     TEXT(EV2(<<EOF));
38 :     If ${BM}f${EM} is the focal length of a convex lens and an object is
39 :     placed at a distance ${BM}p${EM} from the lens, then its image
40 :     will be at a distance ${BM}q${EM} from the lens, where ${BM}f${EM}, ${BM}p${EM}, and ${BM}q${EM}
41 :     are related by the lens equation
42 :     \[ \frac{1}{f} = \frac{1}{p} + \frac{1}{q} \]
43 :     $PAR
44 :     What is the rate of change of ${BM}p${EM} with respect to ${BM}q${EM} if
45 :     ${BM}q = $q ${EM} and ${BM}f = $f${EM}? (Make sure you have the correct sign for the rate. Note that \(f\) is constant.)
46 :     $PAR
47 :     \{ans_rule(20) \}
48 :     EOF
49 :    
50 :     $ans = - $f**2/($q-$f)**2;
51 : gage 269 ANS(num_cmp($ans));
52 : jj 213
53 :     ENDDOCUMENT(); # This should be the last executable line in the problem.

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