3

Here is a MNWE including the following definition with a list but the last item is throwing up problems as described in the title and also the indent of the last bullet isn't indented as the others are;

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\newcommand{\R}{\mathbb{R}}
\newenvironment{definition}{}{}
\begin{document}
\begin{definition}[Two-dimensional curves]
  {It is called a simple arc of a curve, the set $C$ of points $M(x,y) \in \R ^2 $
    (two-dimensional Euclidean space) satisfying one of the following equivalent equations;}
  \begin{itemize}
    \item{
      $ y=f(x), \text{ where } a,b \in \R \text{ and are also fixed} \text{,}$
    }
    \item{
      $ F(x,y)=0, \text{ } a_1 \leq x \leq a_2,\text{ }b_1 \leq y \leq b_2 \text{ where, } a_1, a_2, b_1, b_2 \in \R \text{,}$
    }
    \item{
      $
      \left\{\begin{array}{cll}
        x=g(t)\\
        y=h(t)
      \end{array}\right. \text{, where c_1<t< c_2} \text{ and } c_1,c_2 \in \R
      \text{.}$
    }
  \end{itemize}
\end{definition}
\end{document}
  • 1
    Please provide your code as a complete document which we can try to compile to reproduce the error. Please also give the exact text of the error message. – cfr Nov 20 '16 at 1:33
  • @cfr i can but its now at about 5 pages long? – Sam Harper Nov 20 '16 at 1:34
  • 3
    No not your real document. Make your minimal example complete. I've tried to patch it together, but I can't reproduce the error because I get a different error first. You probably need more preamble. But you also need less preamble: only include packages required to reproduce the error. – cfr Nov 20 '16 at 1:36
  • 2
    Couple of observations. You don't really need braces after \item around the item. I guess you can have them if you want, but I don't think they'd do anything. If you want just a space in math mode, \ is a much better way of getting it than \text{ } and you have an array with columns specified cll, but then you don't put in any &s so the result is just the one centred column – Au101 Nov 20 '16 at 2:00
3

I minimised and completed your example with a dummy environment.

c_1<t< c_2

cannot be set in text mode. It needs to be in maths mode.

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\newcommand{\R}{\mathbb{R}}
\newenvironment{definition}{}{}
\begin{document}
\begin{definition}[Two-dimensional curves]
  {It is called a simple arc of a curve, the set $C$ of points $M(x,y) \in \R ^2 $
    (two-dimensional Euclidean space) satisfying one of the following equivalent equations;}
  \begin{itemize}
    \item{
      $ y=f(x), \text{ where } a,b \in \R \text{ and are also fixed} \text{,}$
    }
    \item{
      $ F(x,y)=0, \text{ } a_1 \leq x \leq a_2,\text{ }b_1 \leq y \leq b_2 \text{ where, } a_1, a_2, b_1, b_2 \in \R \text{,}$
    }
    \item{
      $
      \left\{\begin{array}{cll}
        x=g(t)\\
        y=h(t)
      \end{array}\right. \text{, where }c_1<t< c_2 \text{ and } c_1,c_2 \in \R
      \text{.}$
    }
  \end{itemize}
\end{definition}
\end{document}
  • 2
    You fail to note the big number of infelicities in the code. – egreg Nov 20 '16 at 9:38
  • @egreg Yes, I only fixed the error, it is true. Well, I also turned the original code into a minimal example. The empty definition of the environment was just to get past the error complaining it was undefined. The original loaded amsthm but didn't define definition. I figured the OP could easily restore their original definition, whereas I could not easily add it. (I never use amsthm myself.) – cfr Nov 20 '16 at 13:57
  • 1
    It's not only the missing code for definition: something like \item{$ y=f(x), \text{ where } a,b \in \R \text{ and are also fixed} \text{,}$} is utterly wrong. – egreg Nov 20 '16 at 14:02
  • @egreg - Would you say my code -- \item $y=f(x)$, where $a,b\in\R$ and are also fixed -- is acceptable? :-) – Mico Nov 20 '16 at 14:08
  • @Mico Of course! Although ungrammatical, but that's a problem with the original text. – egreg Nov 20 '16 at 14:19
5

In addition to fixing the immediate issue related to not using math mode for math material (as in @cfr's answer), you should also (a) omit the unnecessary instances of { and } for grouping purposes -- in particular, \item does not take an argument that needs to be enclosed in curly braces --, (b) be more purposeful about using text and math mode -- all those \text statements are actually a sign of code confusion -- and (c) be more circumspect about defining an environment called definition; I suggest you load the amsthm package and use a \newtheorem{definition}{Definition} directive.

enter image description here

Finally, I can't help but comment that there seems to be something missing in two of the three bullet point items: How do a, b, c_1, and c_2 come into play?

\documentclass{article}
\usepackage{amsmath,amssymb,amsthm}
\newcommand{\R}{\mathbb{R}}
\theoremstyle{definition}
\newtheorem*{definition}{Definition}
\begin{document}
\begin{definition}[Two-dimensional curves]
The simple arc of a curve is the set $C$ of points $M(x,y)\in\R^2$ 
(two-dimensional Euclidean space) that satisfy one of the 
following equivalent equations:
  \begin{itemize}
    \item $y=f(x)$, where $a,b\in\R$ and are also fixed,
    \item $F(x,y)=0$, $a_1 \leq x \leq a_2,$ $b_1 \leq y \leq b_2$, 
      where $a_1, a_2, b_1, b_2 \in \R$,
    \item $\begin{cases} x=g(t)\\ y=h(t) \end{cases}$ 
      where $c_1<t<c_2$ and $c_1,c_2\in\R$.
  \end{itemize}
\end{definition}
\end{document}

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