Numbering a reworded theorem

Question

When using LaTeX for numbered theorems (or other numbered environments for that matter), if you have a theorem, and then you want to give a reformulation of the theorem, is there anyway to get LaTeX to number your first theorem, say Theorem 5, and your reformulation as say Theorem 5'?

To obtain numbered theorems, I am not using any package, just using the command

\newtheorem{theorem}{Theorem}

in my preamble.

Answer 1

For a one-off use, perhaps the simplest is to say

\addtocounter{theorem}{-1}% so next theorem will be 5 again then
\begingroup% local redefinition of theorem counter printing
\renewcommand\thetheorem{\arabic{theorem}'}
\begin{theorem}...
\end{theorem}
\endgroup

Or for example wrap it in an environment such as

\newenvironment{alttheorem}
{%
 \addtocounter{theorem}{-1}%
 \renewcommand\thetheorem{\arabic{theorem}'}%
 \theorem}
{\endtheorem}

then use an alttheorem environment after a theorem one.