Equation numbering: how can I get (1.1), (2.1), (3.2) in the article class?

The title of you post is very bad. It is essentially useless for other users that may face a similar issue, when they search for existing questions/answers on this site. That would be nice if you could reformulate it in a more descriptive way, as, for instance: Equation numbering: how can I get (1.1), (2.1), (3.2) in the article class?

2 Answers 2

The question can also be interpreted that the first number of the composite equation number should be the section number. The other two classes report and book are using composite equation numbers, whose first part is the chapter number. The article class does not have chapters and uses plain equation numbers.

Package amsmath (this is used because of align ) provides an easy way to add the section number:

\documentclass \usepackage \numberwithin \begin \section \begin a = a\\ b = b\\ c = c \end \section \begin d = d \end \end