# Increase the fontsize on either the whole document or just a segment

How do you increase the fontsize on either the whole document or preferably just this segment?

 \begin{center}
$R_{ecl} = \sqrt{(X_{ecl}^{2} + Y_{ecl}^{2} + Z_{ecl}^{2})}$\\
$\lambda = \arctan{\frac{Y_{ecl}}{X_{ecl}}}$\\
$\beta = \arctan{\frac{Z_{ecl}}{\sqrt{(X_{ecl}^{2} + Y_{ecl}^{2})}}}$\\
\end{center}

• What's the default font size, and what's the desired font size?
– Mico
Aug 26, 2015 at 18:48
• Unrelated to your question, but you might want to have a look at the amsmath package and its gather environment, e.g. How do I add a line break in display math mode? Aug 26, 2015 at 18:48

For example

 \begin{center}
\large
$R_{ecl} = \sqrt{(X_{ecl}^{2} + Y_{ecl}^{2} + Z_{ecl}^{2})}$\\
$\lambda = \arctan{\frac{Y_{ecl}}{X_{ecl}}}$\\
$\beta = \arctan{\frac{Z_{ecl}}{\sqrt{(X_{ecl}^{2} + Y_{ecl}^{2})}}}$\\
\end{center}


There is also \Large, \LARGE, \huge and \Huge.

Assuming you're using pdfLaTeX, you should primarily be looking at the commands \large, \Large, and \huge. Each command represents a 20% step-up in font size from the preceding level. To localize the effect of the font size change, place the macros either in a pre-defined environment (such as center) or encase them in a pair of \begingroup and \endgroup statements.

\documentclass{article}
\usepackage[vmargin=1cm]{geometry}
\usepackage{amsmath} % for "gather*" environment
\newcommand\threelines{\par
\begin{gather*}
R_{ecl} = \sqrt{X_{ecl}^{2} + Y_{ecl}^{2} + Z_{ecl}^{2}}\\
\lambda = \arctan{\frac{Y_{ecl}}{X_{ecl}}}\\
\beta = \arctan{\frac{Z_{ecl}}{\sqrt{X_{ecl}^{2} + Y_{ecl}^{2}}}}
\end{gather*}}
\begin{document}

\verb+default font size+
\threelines

\begingroup
\large
\verb+20% larger+
\threelines
\endgroup

\begingroup
\Large
\verb+44% larger+
\threelines
\endgroup

\begingroup
\Huge
\verb+73% larger+
\threelines
\endgroup

\end{document}