# How to change equation numbering globally? [duplicate]

I would like to change equation numbering like: (1a) (1b) (1c). How should I do this? My code is like this:

$$first equation with number(1a)$$
$$first equation with number(1b)$$
$$first equation with number(1c)$$

• Welcome to TeX.SX! You should make clear what the fixed number means: is it the section/chapter number or is it the “global number” of the set of equations? In the latter case, follow the link shown by Werner; otherwise \renewcommand{\theequation}{\thesection\alph{equation}} is the way to go. – egreg Oct 19 '15 at 17:23
• Do you want to do this globally, or do you need subeqations? – Johannes_B Oct 19 '15 at 17:30
• I want to do this globally. Thanks for your help – fariba milani Oct 20 '15 at 14:42