--- loncom/html/adm/help/tex/Authoring_Output_Tags.tex 2017/01/23 20:29:42 1.25
+++ loncom/html/adm/help/tex/Authoring_Output_Tags.tex 2021/01/22 17:16:31 1.27
@@ -8,7 +8,8 @@ This group of tags generates useful outp
\begin{verbatim}
2x^y+sqrt(3/x^2)
\end{verbatim}
-Expressions are displayed using the math expression display mechanism defined in the user's preferences. See the section below concerning the $<$m$>$ tag for more information on that as well as on the \textbf{display} attribute.
+Expressions are displayed using the math expression display mechanism for the current context. The default is to use
+the display mechanism the user has selected in preferences. This can be overriden by setting the \textbf{display} attribute for the tag. See the section below concerning the $<$m$>$ tag for more information on how the default is set and on the display attribute.
Recognized functions are all trigonometric functions, and the following:
exp, abs, logten, log, ln, sqrt, sgn, step, fact, int, lim, funX.
@@ -17,8 +18,30 @@ exp, abs, logten, log, ln, sqrt, sgn, st
O2 + 2H2 -> 2H2O
\end{verbatim}
will be rendered:
-
$\mathrm{O_2} + 2\,\mathrm{H_2} \to 2\,\mathrm{H_2O}$
+
+\textbf{Syntax Description}
+\begin{itemize}
+\item Reactants are separated from products by `\texttt{->}'.
+\item Individual reactants and products are separated by `\texttt{ +}' (leading space is obligatory).
+\item Numbers preceding the first symbol of a chemical specie are considered to be stoichiometric coefficients.
+\item Numbers appearing after the first symbol of a chemical specie are considered to be subscripts.
+\item Superscripts are initialized by `\texttt{\^{}}' and terminated by a space.
+\item Ionic charges are superscripts composed of a number followed by a sign (i.e. `\texttt{\^{}2+}').
+\end{itemize}
+
+\textbf{More examples}
+\begin{itemize}
+\item $\mathrm{Ca}(\mathrm{NO}_3)_2$ is written as:\\
+\texttt{Ca(NO3)2}
+\item $\mathrm{OH}^- + \mathrm{H_3O}^+ \to 2\mathrm{H_2O}$ is written as:\\
+\texttt{OH\^{}- + H3O\^{}+ -> 2H2O}
+\item $[\mathrm{Co}(\mathrm{H_2O})_6]^{2+} + 4\mathrm{Cl}^- \to [\mathrm{CoCl_4}]^{2-} + 6\mathrm{H_2O}$ is written as:\\
+\texttt{[Co(H2O)6]\^{}2+ + 4Cl\^{}- -> [CoCl4]\^{}2- + 6H2O}
+\item $^3_1\mathrm{H} + ^2_1\mathrm{H} \to ^4_2\mathrm{He} + ^1_0\mathrm{n}$ is written as:\\
+\texttt{\^{}3 1H + \^{}2 1H -> \^{}4 2He + \^{}1 0n}
+\end{itemize}
+
\item \textbf{num}\index{num}\index{format number}: Typesets a number formatted in scientific notation, fixed point, fixed point with commas, fixed point with commas and dollar sign, or in significant digits.
\begin{verbatim}
31454678 results in 3.15 x 10^7
@@ -153,13 +176,19 @@ to HTML (or MathML) on the fly. The defa
to the display mechanism that the user has selected in preferences. This can be
overriden by setting the attribute \textbf{display} to one of
``\textbf{tth}'', ``\textbf{mimetex}'' or ``\textbf{mathjax}'' which
-will force a specific display mechanism. Note that the ``\textbf{jsmath}'' display is deprecated today, and MathJax is used instead when it is specified.
+will force a specific display mechanism. Note that the ``\textbf{jsmath}'' display is deprecated today, and MathJax is used instead when it is specified. If a display attribute is not included, the display mechanism is determined in the following order, with the first one set being the one in effect:
+\begin{enumerate}
+\item In course context: Course-wide default set by Course Coordinator via Settings $>$ Course Settings $>$ Display of resources $>$ Force use of a specific math rendering engine
+\item User's own personal preference set by the user hovering over the user's name at top left of a LON-CAPA page, and selecting Preferences $>$ Math display settings
+\item Domain default set by a Domain Coordinator
+\item System default set for the LON-CAPA version installed on the server (tth in 2.11 and earlier, mathjax in 2.12).
+\end{enumerate}
The contents of \texttt{ } are interpreted as LaTeX outside math environment, which is why using \texttt{\$ \$} is needed to switch to the LaTeX math environment. However, the ``\textbf{mathjax}'' display (which is used by default in recent versions of LON-CAPA) interprets all the contents of \texttt{ } as math, and does not support non-math LaTeX. For content to work well with all the display mechanisms, it is therefore important to never use non-math LaTeX for web targets. Even purely for printing, it is better to avoid using non-math LaTeX, as the printing mechanism might use HTML instead of LaTeX in the future.
If you want variables inside of this tag to be evaluated before the
tex gets converted, then use eval=``on'' \index{eval=on}. For
-example, \texttt{\$ \$eqn \$},
+example, \texttt{\$ \$eqn \$},
will evaluate the variable \$eqn first and then use the
display mechanism. Anytime you use a variable inside of the m tag,
you will want to set eval to on.
@@ -172,7 +201,7 @@ For example, put the following in a scri
and in a text area, you can type:
-\texttt{\$ \$eqn \$}
+\texttt{\$ \$eqn \$}
You will get the equation rendered with no +-, no matter what value
\$b may take on.