Theorem numbering in LaTeX

Question

I have a problem with theorem numbering in LaTeX. I can make it number by subsection, e.g

Theorem 1.2.1

for the first theorem in

Answer 1

Putting the following code in the preamble seems to have the desired effect:

\usepackage{amsthm}
\newtheorem{thm}{Theorem}[subsection]
\renewcommand{\thethm}{\arabic{subsection}.\arabic{thm}}

I don't understand why you want this particular theorem numbering system, but the code does what you want: