## WeBWorK Problems

### Problem with jsMath?

by Danny Glin -
Number of replies: 5
Hi,
I wasn't sure whether to report this as a bug in the problem, since it's more an issue with jsMath.
Problems such as Library/Rochester/setLinearAlgebra1Systems/ur_la_1_22.pg use the \begin{array}{rrr|r} construction in LaTeX to create a vertical bar within a matrix. When fed to jsMath, this spits the error:
Unknown control sequence '\vbox'
Is there a way to get these bars to appear within jsMath?

### Re: Problem with jsMath?

by Davide Cervone -
JsMath does not do horizontal or vertical lines in matrices, though it should not produce an error -- it should silently ignore the line specifier in the array description. Perhaps there is a \vbox in the body of the array somewhere? Double-clicking the error message to see the original TeX source might help locate that.

Davide

### Re: Problem with jsMath?

by Danny Glin -
The code uses the display_matrix function. The call is:
display_matrix([[1, 0, $c[1]], [0, 1, -$c[2]]], align=>"rr|r")
This leads to the LaTeX code of
for the vertical line.
Does anyone else see this behaviour for this particular problem file?

### Re: Problem with jsMath?

by Danny Glin -
So I just updated to the trunk version of webwork and pg, and I'm still getting this error message. Is this something that can be fixed in jsMath, or will the problems using this construction have to be changed?
Danny

### Re: Problem with jsMath?

by Arnold Pizer -
Hi,

I just edited the trunk version of /opt/webwork/pg/macros/PGmatrixmacros.pl following suggestions of Davide Cervone.

Using this all problems in Rochester/setLinearAlgebra1Systems display nicely in jsMath and images mode.