Math & Science ⇒ Change the Numbering for a Theorem Style Environment

[thedoctor818]

I am using the following (amongst others) theorem-style enviornemnt:

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\theoremstyle{plain}
\newtheorem{thm}{Theorem}[section]

and

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\theoremstyle{definition}
\newtheorem{exc}{Exercise}[section]

Here is my MWE:

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\documentclass[12pt,a4paper,oneside]{report}
\pagestyle{myheadings}
\usepackage{amsmath,amssymb,amscd,amsthm,amstext}

\begin{document}
\title{Real Analysis Notes.}
\author{The Doctor.}
\date{\today}
\maketitle

\begin{exc}
Let $A=\{1,2,3\}$ and let $B=\{3,4,5\}$ Then $A\cupB=\{1,2,3,4\}$ and $a\capB=\{3\}.$
\end{exc}

\end{document}

And then I have many more exercises to come. What I would like to do is to have the numbering of these exercises begin with 1.1.13 to match the homework assignment our Professor has given us from textbook. Thanks for any help.

[frabjous]

You can set the counters manually.

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\setcounter{chapter}{1}
\setcounter{section}{1}
\setcounter{exc}{12}

[thedoctor818]

When I do that, I ge the following error message:

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LaTeX Error: No counter 'exc' defined.

[frabjous]

Did you remember to put the:

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\theoremstyle{definition}
\newtheorem{exc}{Exercise}[section]

lines back in? (They were missing from your mwe). I also had to fix \capA and \cupB to \cap A and \cup B.

Try this mwe:

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\documentclass[12pt,a4paper,oneside]{report}
\pagestyle{myheadings}
\usepackage{amsmath,amssymb,amscd,amsthm,amstext}
\theoremstyle{plain}
\newtheorem{thm}{Theorem}[section]
\theoremstyle{definition}
\newtheorem{exc}{Exercise}[section]
\begin{document}
\title{Real Analysis Notes.}
\author{The Doctor.}
\date{\today}
\maketitle

\setcounter{chapter}{1}
\setcounter{section}{1}
\setcounter{exc}{12}

\begin{exc}
Let $A=\{1,2,3\}$ and let $B=\{3,4,5\}$ Then $A\cup B=\{1,2,3,4\}$ and $a\cap B=\{3\}.$
\end{exc}

\end{document}

Compiles fine for me.

[thedoctor818]

Just one more question. That is, how would I get the first example to be Example 1.1.13? Thanks for all your help. -MD

[frabjous]

Do you mean Example, or Exercise? My sample already starts at Exercise 1.1.13. If you mean Example, then give us a mwe code that provides/uses this environment.

[thedoctor818]

Thanks a lot. Now, I need to stop the list at some Excercise num, then restart at Excercise num 1.2.7 - how can I accomplish this. Thanks a lot, again. -MD

[frabjous]

Either insert a \section{...} command, or \stepcounter{section} to advance the section number, and \setcounter{exc}{6} to push the exercise number back to 6 (so that the next one is 7).

[thedoctor818]

OK, thanks that has solved my problem. I appreciate it a lot. -MD