\documentclass[12pt,oneside]{book} \usepackage[a4paper,textwidth=16.5cm,textheight=23cm,bindingoffset=1cm]{geometry}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{caption}
\usepackage{amsfonts,amsmath,amssymb,amsthm,mathrsfs}
\usepackage{fancyhdr}
\usepackage{hyperref}
\hypersetup{colorlinks=true, linkcolor=blue, urlcolor=blue}
\newtheorem{theorem}{Theorem}
\newtheorem{corollary}{corollary}
\newtheorem{definition}{Definition}
\newtheorem{lemma}{Lemma}
\newtheorem{proposition}{Proposition}