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Bill Ziemer - Error in problem:

Bill Ziemer - Error in problem:

by Arnold Pizer -
Number of replies: 0
inactiveTopicError in problem: topic started 9/23/2003; 5:28:19 PM
last post 12/31/2003; 5:13:40 PM
userBill Ziemer - Error in problem:  blueArrow
9/23/2003; 5:28:19 PM (reads: 1032, responses: 5)
From the Rochester library


Seed 1320

gives the incorrect answer. Other seeds are fine.

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userCoreen Mett - Re: Error in problem:  blueArrow
9/25/2003; 10:04:42 PM (reads: 1187, responses: 0)

In about line 182 the evaluator

     num_cmp(int( f_rule( g_rule($xg-.00001) )) ) ,

needs to be changed to 

    num_cmp(rnd( f_rule( g_rule($xg-.00001) )) ) ,


Now for a question:  How does one make sure that the problem gets corrected in the distribution of *.pg files?




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userBill Ziemer - Re: Error in problem:  blueArrow
9/26/2003; 2:41:04 AM (reads: 1189, responses: 0)
This exact question, and the need for a solution, is the basis for the construction of a national webwork problem database. Jeff Holt, John Jones, and I have submitted an NSF grant to do this. It should be coming, soon if the grant is funded.

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userArnold K. Pizer - Re: Error in problem:  blueArrow
9/26/2003; 8:44:20 AM (reads: 1201, responses: 0)


Hopefully Bill, Jeff, and John's proposal will be funded and we will have a robust national webwork problem database.

Until that time the best thing to do is to report bugs here (or to and we will attempt to fix the bug.  If you want to speed solutions, please send us bug fixes (thanks Coreen).

In this particular  case, I have changed

"int("    to    "rnd(" 

in two places (lines 175 and 180 of setLimitsRates1_5Graphs/ You can get the corrected version from

The corrected version will be included in the next distribution of .pg files.


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userThomas R. Shemanske - Re: Error in problem:  blueArrow
9/26/2003; 3:39:27 PM (reads: 1196, responses: 1)
We seem to have another one of the same type, but for which the "int" to "rnd" trick did not work

setLimitRates2Limits/ with seed 4525


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userThomas R. Shemanske - Re: Error in problem:  blueArrow
12/31/2003; 5:13:40 PM (reads: 1303, responses: 0)
I took some time to look at this problem now that the term is over.  There is no error.

The given problem is lim_{xto 0^+} f(g(x))

A quick glance at the graph of g show that is goes to zero (through positive values) as x -> 0^+, so one evaluates lim_{zto 0^+) f(z)

Sadly, it is the resolution of the graph that causes the problem.  If you *really* stare at in, it appears as though the graph of g dips just below the x-axis right near the origin.  In fact that is the case, so one really has to evaluate lim_{zto 0^-} f(z) for the correct answer

Setting the size=>[400,400] options in the graphs allows enough resolution to discern this more easliy.


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