Equations, change the font size

Question

How do I change the font size of something like this: I want to increase the font but it always seems to remain the same.

 \documentclass[30pt]{article}
 \DeclareMathSizes{20}{20}{20}{20}
 \begin{document}

 \[
   x = \frac{1}{x + \frac{1}{x + \frac{1}{x}}}
 \]

 \end{document}

Answer 1

The first parameter of \DeclareMathSizes specifies the font size to which these settings are applied to. So, for a 12pt document, if the first parameter is not 12, then this command will have no effect. So for the code as below, the output is:

but with the line \DeclareMathSizes{12}{24}{24}{24} un-commented you get:

Also see How to make math font huge.

\documentclass[12pt,border=5pt]{standalone}
% \DeclareMathSizes{12}{24}{24}{24}% Uncomment to see the effect
\begin{document}
\[
   x = \frac{1}{x + \frac{1}{x + \frac{1}{x}}}
\]
\end{document}

Answer 2

no need to redefine the math sizes: use \dfrac from amsmath

\documentclass{article}
\usepackage{amsmath}
 \begin{document}

 \[
   x = \dfrac{1}{x + \dfrac{1}{x + \dfrac{1}{x}}}
 \]
\Huge
 \[
   x = \dfrac{1}{x + \dfrac{1}{x + \dfrac{1}{x}}}
 \]

 \end{document}