Hi guys! One question (my friend asked me): why here http://i.imgur.com/ctQMi7T.png symbols like \in, +, \neq looks so small (or strange, at least for me and friend)? I can give you his first part of code
\documentclass[a4paper,10pt]{book}
\usepackage[utf8x]{inputenc}
\usepackage[LGR,T1,T2A]{fontenc}
%\usepackage[T1,T2A]{fontenc}
\usepackage[serbian]{babel}
\usepackage{fullpage}
\usepackage{datetime}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{MnSymbol}
\usepackage[none]{hyphenat}