4

pdflatex keeps complaining about braces but they are balanced. I read that some environments start math mode automatically, but I don't think I'm using them.

Here is the code:

\documentclass{article}

\title{Analisi I - Teoremi}
\date{\today}
\usepackage{amsthm}

\begin{document}
\maketitle
\newpage

\section{Limit Infiniti}
\newtheorem*{perm}{Teorema della permanenza del segno}
\begin{perm}
    Sia $\lim_\limits{x \to \alpha} f(x) = +\infty$ e $a > 0$. Allora esiste
    una semiretta su cui $f(x) > a > 0$.
\end{perm}
\begin{proof}
    Segue immediatamente dalla definizione. \qedhere
\end{proof}

\newtheorem*{confronto}{Teorema del confronto}
\begin{confronto}
    Sia $\lim_\limits{x \to \alpha} f(x) = +\infty$ e $g(x) \geq f(x)$. Allora
    $\lim_\limits{x \to \alpha} g(x) = +\infty$.
\end{confronto}
\begin{proof}
    \\[
        \begin{cases}
            f(x) &> \epsilon\\
            g(x) &\geq f(x)
        \end{cases} \implies g(x) > \epsilon
    \\]
\end{proof}
% section Limit Infiniti (end)

\end{document}
  • @HarishKumar Unfortunately the problem persists. – rubik Feb 1 '15 at 14:49
6

This is what went wrong:

  1. You didn't load amsmath but used cases.
  2. \lim_\limits{x... should be \lim\limits_{x.. i.e, _ should come after \limits not before.
  3. You have used \\[....\\] for display equation which should be \[....\]

Corrected code:

\documentclass{article}
\usepackage{amsmath}

\title{Analisi I - Teoremi}
\date{\today}
\usepackage{amsthm}

\begin{document}
\maketitle
\newpage

\section{Limit Infiniti}
\newtheorem*{perm}{Teorema della permanenza del segno}
\begin{perm}
    Sia $\lim\limits_{x \to \alpha} f(x) = +\infty$ e $a > 0$. Allora esiste
    una semiretta su cui $f(x) > a > 0$.
\end{perm}
\begin{proof}
    Segue immediatamente dalla definizione. \qedhere
\end{proof}

\newtheorem*{confronto}{Teorema del confronto}
\begin{confronto}
    Sia $\lim\limits_{x \to \alpha} f(x) = +\infty$ e $g(x) \geq f(x)$. Allora
    $\lim\limits_{x \to \alpha} g(x) = +\infty$.
\end{confronto}
\begin{proof}
    \[
        \begin{cases}
            f(x) > \epsilon\\
            g(x) \geq f(x)
        \end{cases} \implies g(x) > \epsilon
    \]
\end{proof}
% section Limit Infiniti (end)

\end{document}

The format for cases is

<case> & <condition>

and since you don't have any conditions here, no need of using & here and f(x) > \epsilon gives proper spacing.

  • Great, thanks for your help. I forgot about amsmath – rubik Feb 1 '15 at 14:57

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