How to scale all mathematics of a document [duplicate]

Possible Duplicate:
Equations, change the font size
How to scale math font only

I am very new to LaTeX. I want all mathematics(i.e. the thing we write inside $...$ and $...$) of my document to be shown larger than the other texts. How can I do it?

edit:here is an worked example:

\documentclass[14pt]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage[xetex]{graphicx}
\usepackage{fontspec}
\usepackage[margin=2cm]{geometry}

%Defining fonts
\font\e="Times New Roman" at 12pt
\font\lb="SolaimanLipi-Bold:script=beng" at 22pt
\font\b="SolaimanLipi:script=beng" at 14pt
\font\bl="SolaimanLipi-Bold:script=beng" at 14pt
\begin{document}
\title{\lb{অণুসম গণিত}}
\date{}
\maketitle
\b{নাম্বার থিয়োরি ভালোবাসেন কিন্তু কনগ্রুয়েন্স বা অনুসমতা সম্পর্কে ধারণা নেই এমন মানুষ একটিও সম্ভবত এই ধরাধামে খুঁজে পাওয়া যাবে না। কারণ ক্লাসিক্যাল নাম্বার থিয়োরির খুব বড় একটি অংশই যে রয়েছে এই মডুলার এরিথম্যাটিকের দখলে।

এবার ভূমিকা ছেড়ে মূল আলোচনায় আসা যাক। $a$ এবং $b$ সংখ্যা দুটিকে যদি $c$ দ্বারা ভাগ করে একই ভাগশেষ পাওয়া যায় তবে বলা হয়} \bl{$a$ এবং $b$ হচ্ছে $c$ ভাজকের সাপেক্ষে অনুসম বা কনগ্রুয়েন্ট।} \b{কিংবা গণিতের ভাষায় $a\equiv b\; (\bmod\; c)$}
\b{ পড়তে হয়} '\e{$a$ is congruent to $b$ modulo $c$}'
\end{document}

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marked as duplicate by Hendrik Vogt, Thorsten, Kurt, Claudio Fiandrino, lockstepJan 28 '13 at 19:07

Welcome to TeX.sx! – Peter Jansson Jan 28 '13 at 11:21
Can I ask why you want to do so? Because I'm sure it won't look pleasantly at all. – yo' Jan 28 '13 at 11:25
yeah, I know. Actually I'm using XeTeX to write in Unicode. While using it I found that all mathematics are in 10pt size and whenever I change the font size of the whole document, it does not apply to the font size of mathematics. That's why I was wondering if there is any way to control the size of only mathematics. – Neehan Jan 28 '13 at 11:34
Have you tried using the 12pt option to the documentclass as in \documentclass[12pt]{article} ? – Nasser Jan 28 '13 at 11:43
There is no 14pt option for the article class, so you end up with the default 10pt. Using \font in LaTeX is never a good idea: use the facilities of fontspec for that. – egreg Jan 28 '13 at 12:03

There are several problems with your code.

To get the article class with the 14pt option you need to use extarticle instead.

Using the \font command is not the recommended way of working with fontspec. It is better to load the font families and then use sizing commands of LaTeX, e.g. \large etc. or for other sizes \fontsize{a}{b}\selectfont, where a is the desired fontsize in points and b is the baselineskip.

Thirdly there is a problem with math scaling if you use standard latex set-up at large sizes. This is corrected by the fix-cm package.

Below is an example using a non-exotic font:

\documentclass[14pt]{extarticle}

\usepackage{amssymb,amsfonts,fix-cm}
\usepackage{fontspec}

\fontspec{Times New Roman}

\begin{document}
{$a$ is congruent to $b$ modulo $c$}

\medskip

{\fontsize{100}{106}\selectfont Huge $a$ is congruent to $b$ modulo $c$\par }
\end{document}


For your other fonts, consider using the \newfontfamily as follows:

\newfontfamily{\lipi}[Script=beng}{SolaimanLipi}


I don't have this font available to test, but if all is well you should be able to use \lipi to switch to this collection of fonts and use \textbf etc. to change to bold versions. If these are to be the main document fonts, then load them with the \fontspec command instead, and define a separate command for the Times New Roman instead.

Now if you still really want the mathematics to be bigger than the standard text you can use fontspec via unicode-math in the following type of way, loading your choice of math font with an extra Scale option:

\documentclass[14pt]{extarticle}

\usepackage{unicode-math}

\setmathfont[Scale=2.5]{xits-math.otf}
\setmainfont{Times New Roman}

\begin{document}
$a$ is congruent to $b$ modulo $c$

\medskip

{\fontsize{30}{34}\selectfont Huge $a$ is congruent to $b$ modulo
$c$}

\end{document}


Of course, with this exaggerated maths scaling the sizing command should probably be more like \fontsize{30}{80} to allow space for the large characters.

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+1 I also stole your example to use in my answer (which relies on having fonts set up right as you note here) – David Carlisle Jan 28 '13 at 14:22
@DavidCarlisle Thanks - the final part of my answer was delayed by not knowing that xelatexs way of finding fonts - lualatex is so much easier. The example phrase used is actually from the end of the poster's code. – Andrew Swann Jan 28 '13 at 14:32

Your example uses primitive \font commands which cut through the LaTeX font mechanism. If you don't do that and always declare fonts via latex font declaration commands then the size of fonts used in mathematics is controlled by \DeclareMathSizes For example this declares that if the text font is 12pt then the math font should be 20pt (and 16pt in subscripts and 12pt in subsubscripts)

\documentclass[12pt]{article}

\usepackage{amssymb,amsfonts,fix-cm}
\usepackage{fontspec}

\fontspec{Times New Roman}
\DeclareMathSizes{12}{20}{16}{12}

\begin{document}
$a$ is congruent to $b$ modulo $c$

\end{document}

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I'll let this answer stand as it answers the original question and may be useful to others. However as clarified in comments you do not want to do this. The reason that the math and text fonts were not at the same size was that you were using primitive font commands so not giving font LaTeX mechanisms any information. If you declare the sizes using LaTeX declarations as in the other two answers math and text will match. – David Carlisle Jan 29 '13 at 12:31

If you really want 14pt main size, use extarticle; since your default language seems Bengali, it's better to use Polyglossia:

\documentclass[14pt]{extarticle}
\usepackage{amsmath}

\usepackage{unicode-math}

\setmainfont{FreeSerif}
\newfontfamily{\termes}[Ligatures=TeX]{TeX Gyre Termes}
\setmathfont{TG Termes Math}

\usepackage{polyglossia}
\setmainlanguage{bengali}
\setotherlanguage{english}

\newcommand{\bl}[1]{#1} % the FreeSerif font doesn't have bold face
% \newcommand{\bl}[1]{\textbf{#1}} % uncomment this for your font

\newcommand{\eng}[1]{\foreignlanguage{english}{\termes #1}}

\begin{document}

\title{অণুসম গণিত}
\date{}
\maketitle

নাম্বার থিয়োরি ভালোবাসেন কিন্তু কনগ্রুয়েন্স বা অনুসমতা সম্পর্কে ধারণা নেই এমন
মানুষ একটিও সম্ভবত এই ধরাধামে খুঁজে পাওয়া যাবে না। কারণ ক্লাসিক্যাল নাম্বার
থিয়োরির খুব বড় একটি অংশই যে রয়েছে এই মডুলার এরিথম্যাটিকের দখলে।

এবার ভূমিকা ছেড়ে মূল আলোচনায় আসা যাক। $a$ এবং $b$ সংখ্যা দুটিকে যদি $c$
দ্বারা ভাগ করে একই ভাগশেষ পাওয়া যায় তবে বলা হয় \bl{$a$ এবং $b$ হচ্ছে
$c$ ভাজকের সাপেক্ষে অনুসম বা কনগ্রুয়েন্ট।} কিংবা গণিতের ভাষায় $a\equiv b \pmod{c}$ পড়তে হয় \eng{$a$ is congruent to $b$ modulo
$c$'}

\end{document}
`

I've got no other Bengali font, so I disabled boldface, which isn't available with FreeSerif.

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+1 As I note in a comment on my answer, I answered the original question as written, but this is what the OP should do (as clarified in comments on the question). – David Carlisle Jan 29 '13 at 12:32