Math & Science ⇒ understand a bit of code

[stepec]

I've just lifted and slightly amended some code from a previous post which numbers some equations the way I want them to. It goes like this.

Code: Select all

\subsection*{Exercise 1}
\renewcommand{\theequation}{1.\arabic{equation}}
\begin{equation}
a
\end{equation}
\begin{equation}
b
\end{equation}

\subsection*{Exercise 2}

\renewcommand{\theequation}{2.\arabic{equation}}
\setcounter{equation}{0}
\begin{equation}
c
\end{equation}
\begin{equation}
d
\end{equation}

I'm not a programmer or even especially computerate, and I don't understand what the line

\renewcommand{\theequation}{2.\arabic{equation}}

actually does. Could somebody enlighten me?

stepec

[Stefan Kottwitz]

Hi stepec!

• equation is the name of the counter for the equation-environment.
• \theequation is the command that prints the equation counter.
• \arabic is a command that takes a counter and outputs its value in arabic numbers.
• \renewcommand redefines an existing command.

So,

Code: Select all

\renewcommand{\theequation}{2.\arabic{equation}}

redefines the output of the equation counter in that way: number 2, followed by a dot and by the number of the equation.

Stefan

[stepec]

Stefan

Thank you very much. I think I get most of that!

I've realised that I'm going to need to number some equations (actually, answers to questions) as question parts - eg 3.1(a), 3.1(b) etc. So I think I'm going to have to create a sub-subsection for the particular question, and use the same bit of code, except instead of {2.\arabic{equation}} I shall have to use {3.1\something{equation}}, where the something = whatever produces (a), (b) etc. I shall have a go, anyway, and see what transpires.

Thanks again.

stepec