\documentclass[a4paper, 12pt]{article} \usepackage[ngerman]{babel} \usepackage[ansinew]{inputenc} \usepackage{amsmath} \usepackage{amssymb} \usepackage{graphics} \usepackage{graphicx} \usepackage{trfsigns} \usepackage{trfsigns} \usepackage{fancybox} \usepackage[table]{xcolor} \usepackage{framed} \usepackage{eurosans} \usepackage{wrapfig} \begin{document} \begin {equation}$$$ \underbrace{ \frac{a_{0}}{2} \underbrace{ \int \limits_{0}^{2 \pi } \cos (m x) dx }_{0}}{0}+\sum_{n=1}^{\infty} \left[\underbrace{ a_{n}\cdot \underbrace{ \int \limits_{0}^{2 \pi } \cos (n x) \cdot \cos(m x) dx}{0| \pi}+ b_{n}\cdot \underbrace{ \int \limits_{0}^{2 \pi } \sin (n x) \cdot \cos (m x) dx}{0|0}}{0|a_{n}\pi }\right] $$$ \end{equation} \end{document}
Anna