LaTeX Tips:



1. To have the style of numbering of equations like: 

(1.3)      A=B
 
\renewcommand{\theequation}{%
\thesection.\arabic{equation}} 
\@addtoreset{equation}{section}


2. To make the style of numbering of theorems in the appendix like:

Theorem A.2 ...... 



\newtheorem{th}{Theorem}[section]
.
.
.
.
.
\renewcommand{\theequation}{A.\arabic{equation}}
\renewcommand{\thesection}{A}
\setcounter{th}{0}
\setcounter{equation}{0}