[texhax] About MathTex

[bnb at ams.org]

On Fri, 28 Nov 2014, Nimble Song wrote:

    Hi,
    	This Day,I found some Latex math expression can`t parses when I use the Matex cgi.
    Here is some example of those latex math expression.And I will be happy if you can reply me as soon as possible .
    	Thanks!
    
    Nimble

first of all, you need
  \usepackage{amsmath}
to handle the gathered environment.
    
    e.g.1:
    \[{{\mathbf{u}}^\operatorname{s}}=\left\{\begin{gathered}{f_1}(t)(z-H)\hfill\\{f_4}(t)z\hfill\\\end{gathered}\right\}+\left\{\begin{gathered}{f_3}(t)\hfill\\{f_2}(t)\hfill\\\end{gathered}\right\}\]

the first part of this has a bad syntax error.
instead of
  {{\mathbf{u}}^\operatorname{s}}
this should be
  {\mathbf{u}}^{\operatorname{s}}
in fact, the braces around \mathbf{u} aren't
needed, since \mathbf takes an argument, so
the bold won't persist beyond the closing
brace of the argument.  \operatorname{s} is
not a single token, hence it *does* need to
be put in braces.

    e.g.2:
    \[{{\mathbf{G}}_1}=\left\{\begin{gathered}{G_{11}}\hfill\\{G_{12}}\hfill\\\end{gathered}\right\}=\left\{\begin{gathered}{C_w}\hfill\\C_v^wA-1\hfill\\\end{gathered}\right\},{{\mathbf{G}}_2}=\left\{\begin{gathered}{G_{21}}\hfill\\{G_{22}}\hfill\\\end{gathered}\right\}=\left\{\begin{gathered}{C_w}\hfill\\C_v^wB-1\hfill\\\end{gathered}\right\}\]

this one does work as shown.

however, the "style" of latex coding is not
the best.  unfortunately, many of the examples
shown on sites with such material neither
exhibit "best practices" nor have undergone
validation or editing.
						-- bb