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

There's no easy way to do this. The AMS Theorem Package only provides a way to control when numbering resets (section, subsection), if it's tied to other environments (corollary, lemma) and number order ("1.1 Theorem" vs. "Theorem 1.1").

Theorem's get their numbering from the \thesection or \thesubsection command. You can redefine the \thesubsection command to get the numbering you want, but that will also affect everything else that uses \thesubsection.