Numbering equations

Question

If I am writing a LaTeX document on TexMaker and I want to number my equation but most probably I will be adding details later on and I do not want to fall into retyping it all over again. So if for example I have an equation and currently called equation (1.2) that I want to refer later as in the following sentence "As you can see in (1.2)" but then I had to edit my document in a way that it becomes (1.3) now instead of (1.2) what should I do in order to avoid editing large number of equations and my reference to them?

Answer 1

LaTeX supports this cross-referencing mechanism out-of-the-box. Fundamentally you should use

\begin{equation}
  <your equation here> \label{<label>}
\end{equation}

for single-line equations, and amsmath's align-style environment for multi-line equations (you can also use it for single-line equations). For example,

\begin{align}
  <eqn 1 LHS> & <eqn 1 RHS> \label{<label1>} \\
  <eqn 2 LHS> & <eqn 2 RHS> \label{<label2>} \\
  ...
\end{align}

See the mathmode document for a host of examples on the amsmath align-environment usages, as well as others.

The above allows you to use \ref{<label>} inside your document to obtain the number/label associated with <label>. It's better to \usepackage{amsmath} and to use \eqref{<label>} just because this includes the (..).

\labels are stored in the .aux, and may only settle after a second compilation. So, if things move around, make sure to compile twice. See Understanding how references and labels work.

If you want to change the numbering of the equations (from say (1.1) to (1)), see Continuous v. per-chapter/section numbering of figures, tables, and other document elements. The chngcntr package is useful for adjusting the resetting of the numbering scheme.