\documentclass{book}
%\documentclass[reqno,16pt]{Book}
\usepackage[colorlinks=true]{hyperref}
\usepackage{graphicx,amsmath,amsbsy,mathtools,amssymb,amsthm,amscd,amsfonts,amsxtra}
\usepackage{xcolor}
\usepackage{subfigure}
\usepackage{breqn}



%\usepackage{comment}
\usepackage{verbatim}
\usepackage{xepersian}

%\usepackage[Lenny]{fncychap}

\settextfont[Scale=1.1]{XB Niloofar}
\setlatintextfont[Scale=1.1]{Times New Roman} 
\setdigitfont[Scale=1.1]{Yas} 
%\renewcommand{\showlabelfont}{\small\slshape\color{blue}}
\renewcommand{\theequation}{\thesection.\arabic{equation}}
\numberwithin{equation}{section} 

\begin{comment}
\[
\lambda\left(t\right) = \alpha_{1}\left(t\right)+\mathrm{i} \beta_{1}\left(t\right)
\]
\end{comment}