## LaTeX forum ⇒ Text Formatting ⇒ Refer to Theorem that contains several Parts

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Mohsen Avaji
Posts: 14
Joined: Mon Aug 27, 2012 12:06 am

### Refer to Theorem that contains several Parts

Hi,

in books and papers often a theorem contains several parts, labeled (i), (ii), ...
\begin{theorem}   Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:   \begin{itemize}     \item[(i)] $f$ is injective.     \item[(ii)] $f$ is surjective.     \item[(iii)] $f$ is a bijection.   \end{itemize}\end{theorem}

I want refer to part(i) of this theorem but I do not know how to do it. How can I do that? I'd be very grateful for any help.
Last edited by localghost on Mon Jun 24, 2013 9:53 am, edited 1 time in total.
Reason: Source code has to be tagged as such to keep a post clear and legible (see Board Rules).
Yours faithfully,
Mohsen Avaji.

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localghost
Site Moderator
Posts: 9204
Joined: Fri Feb 02, 2007 12:06 pm
Please get used to always preparing a self-contained and minimal example. People are rarely motivated to write one on their own just to test solutions for you.

In your case you are better with using an {enumerate} environment instead of {itemize}. It can be customized easily by enumitem. The single list items can be referenced by the common mechanism of the \label and \ref commands.
\documentclass[11pt]{article}\usepackage[T1]{fontenc}\usepackage{enumitem} \newtheorem{theorem}{Theorem} \begin{document}   \begin{theorem}     Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:     \begin{enumerate}[label={(\roman*)},itemindent=1em]       \item $f$ is injective. \label{thm:injective}       \item $f$ is surjective. \label{thm:surjective}       \item $f$ is a bijection. \label{thm:bijection}     \end{enumerate}   \end{theorem}    Reference to item \ref{thm:surjective}.\end{document}

For a deeper understanding of the involved packages take a look at their manuals.

Thorsten
LaTeX Community Moderator

¹ System: openSUSE 42.2 (Linux 4.4.52), TeX Live 2016 (vanilla), TeXworks 0.6.1

Mohsen Avaji
Posts: 14
Joined: Mon Aug 27, 2012 12:06 am
localghost wrote:In your case you are better with using an {enumerate} environment instead of {itemize}. It can be customized easily by enumitem. The single list items can be referenced by the common mechanism of the \label and \ref commands.
\documentclass[11pt]{article}\usepackage[T1]{fontenc}\usepackage{enumitem} \newtheorem{theorem}{Theorem} \begin{document}   \begin{theorem}     Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:     \begin{enumerate}[label={(\roman*)},itemindent=1em]       \item $f$ is injective. \label{thm:injective}       \item $f$ is surjective. \label{thm:surjective}       \item $f$ is a bijection. \label{thm:bijection}     \end{enumerate}   \end{theorem}    Reference to item \ref{thm:surjective}.\end{document}

For a deeper understanding of the involved packages take a look at their manuals.
Thorsten

Hi
In the following I have used ‎\usepackage{theoremref},‎‎ this package refer to theorem with number (in the following example \thref refer to theorem "Theorem 1")
but I want refer to part(i) of theorem by the common mechanism of the \label and \ref and after run have ("Theorem 1(i)").
Any suggestion is appreciated.

Best,
Mohsen
     \documentclass[11pt]{article}     \usepackage[T1]{fontenc}     \usepackage{enumitem}     \usepackage{theoremref}     \newtheorem{theorem}{Theorem}      \begin{document}       \begin{theorem}\thlabel{theorem}         Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:         \begin{enumerate}[label={(\roman*)},itemindent=1em]           \item $f$ is injective. \label{thm:injective}           \item $f$ is surjective. \label{thm:surjective}           \item $f$ is a bijection. \label{thm:bijection}         \end{enumerate}       \end{theorem}      Reference to theorem \thref{theorem}.     \end{document}
Yours faithfully,
Mohsen Avaji.

localghost
Site Moderator
Posts: 9204
Joined: Fri Feb 02, 2007 12:06 pm
Mohsen Avaji wrote:[…] but I want refer to part(i) of theorem by the common mechanism of the \label and \ref and after run have ("Theorem 1(i)"). […]

Any reason against writing it this way?
Reference to \thref{thm:theorem}\ref{thm:surjective}.
LaTeX Community Moderator

¹ System: openSUSE 42.2 (Linux 4.4.52), TeX Live 2016 (vanilla), TeXworks 0.6.1