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Mohsen Avaji
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Refer to Theorem that contains several Parts

Postby Mohsen Avaji » Mon Jun 24, 2013 12:58 am

Hi,

in books and papers often a theorem contains several parts, labeled (i), (ii), ...
  1. \begin{theorem}
  2. Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:
  3. \begin{itemize}
  4. \item[(i)] $f$ is injective.
  5. \item[(ii)] $f$ is surjective.
  6. \item[(iii)] $f$ is a bijection.
  7. \end{itemize}
  8. \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
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Postby localghost » Mon Jun 24, 2013 10:05 am

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.
  1. \documentclass[11pt]{article}
  2. \usepackage[T1]{fontenc}
  3. \usepackage{enumitem}
  4.  
  5. \newtheorem{theorem}{Theorem}
  6.  
  7. \begin{document}
  8. \begin{theorem}
  9. Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:
  10. \begin{enumerate}[label={(\roman*)},itemindent=1em]
  11. \item $f$ is injective. \label{thm:injective}
  12. \item $f$ is surjective. \label{thm:surjective}
  13. \item $f$ is a bijection. \label{thm:bijection}
  14. \end{enumerate}
  15. \end{theorem}
  16.  
  17. Reference to item \ref{thm:surjective}.
  18. \end{document}

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


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

Postby Mohsen Avaji » Mon Jun 24, 2013 9:12 pm

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.
  1. \documentclass[11pt]{article}
  2. \usepackage[T1]{fontenc}
  3. \usepackage{enumitem}
  4.  
  5. \newtheorem{theorem}{Theorem}
  6.  
  7. \begin{document}
  8. \begin{theorem}
  9. Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:
  10. \begin{enumerate}[label={(\roman*)},itemindent=1em]
  11. \item $f$ is injective. \label{thm:injective}
  12. \item $f$ is surjective. \label{thm:surjective}
  13. \item $f$ is a bijection. \label{thm:bijection}
  14. \end{enumerate}
  15. \end{theorem}
  16.  
  17. Reference to item \ref{thm:surjective}.
  18. \end{document}

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

Hi
Thank you for your help.
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
  1. \documentclass[11pt]{article}
  2. \usepackage[T1]{fontenc}
  3. \usepackage{enumitem}
  4. \usepackage{theoremref}
  5. \newtheorem{theorem}{Theorem}
  6.  
  7. \begin{document}
  8. \begin{theorem}\thlabel{theorem}
  9. Let $A$ be a finite set and $f$ a map from $A$ to itself. The following statements are equivalent:
  10. \begin{enumerate}[label={(\roman*)},itemindent=1em]
  11. \item $f$ is injective. \label{thm:injective}
  12. \item $f$ is surjective. \label{thm:surjective}
  13. \item $f$ is a bijection. \label{thm:bijection}
  14. \end{enumerate}
  15. \end{theorem}
  16. Reference to theorem \thref{theorem}.
  17. \end{document}
Yours faithfully,
Mohsen Avaji.

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localghost
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Postby localghost » Mon Jun 24, 2013 9:29 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?
  1. Reference to \thref{thm:theorem}\ref{thm:surjective}.
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