How to properly resize a matrix?

Question

Apparently text is resized in one way and math in other way. However, the commands to resize math do not work well on a matrix; it appears barely smaller and unexpectedly shifted down. The commands to resize text also "work well" to resize a matrix except that it give a warning that you are doing it wrong.

LaTeX Font Warning: Command \scriptsize invalid in math mode on input line 16.

So, what is a proper way to resize a matrix that actually works?

\documentclass[12pt]{article}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}

\begin{document}
 Properly resize variable: $x$ $\scriptscriptstyle{x}$

 Properly resize matrix: $\begin{bmatrix}a & b\\ c & d\end{bmatrix}$ $\scriptscriptstyle{\begin{bmatrix}a & b\\ c & d\end{bmatrix}}$

 Improperly resize matrix: $\begin{bmatrix}a & b\\ c & d\end{bmatrix}$ $\scriptsize{\begin{bmatrix}a & b\\ c & d\end{bmatrix}}$
\end{document}

Answer 1

1. Size changing commands such as \small or \scriptsize are invalid in math mode.

2. \scriptstyle and \scriptscriptstyle are not commands with an argument; writing $\scriptstyle<formula>$ or $\scriptstyle{<formula>}$ has exactly the same result.

3. Neither $\scriptsize\begin{bmatrix}...\end{bmatrix}$ nor $\scriptstyle\begin{bmatrix}...\end{bmatrix}$ work, as you experimented

4. If you need small matrices there's the smallmatrix environment (with amsmath that you're already loading).

5. Another way (not that I recommend it) is to say \mbox{\scriptsize$\begin{bmatrix}...\end{bmatrix}$} inside a math formula.