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cleanup and formatting with a few clarifications

\label{Calling_Functions}

With variables, you can store strings or numbers. \textbf{Functions} allow
you to manipulate these strings or numbers. Functions work like mathematical
functions: They take some number of arguments in, and return one argument,
usually a number or a string for our purposes. There are a lot of functions
available in LON-CAPA. You can see a complete list in the Script section 
\ref{Script_Functions} and LON-CAPA function section \ref{Problem_LON-CAPA_Functions}.

For now, let's just look at some simple examples.

%
\begin{figure}
\$a~=~-3.0;

\$b~=~\&sin(\$a);

\$c~=~\&pow(3.0,~\&abs(\$a));

\caption{Some Function Calls\label{Some Function Calls Figure}}
\end{figure}
In the \textbf{Script} block, function names start with \textbf{\&}. Some
example function calls are shown above.
You can see that functions can take either variables, numbers, or the results
of other function calls as parameters. The \texttt{\&sin} function returns
the sine of an angle expressed in radians. \texttt{\&pow} raises the first
parameter to the power of the second parameter. \texttt{\&abs} returns the
absolute value of the argument.