# Decrease the size of a fraction

I use the following codes

  \documentclass[12pt,a4paper]{article}
%------------------------------------------------------------
\usepackage{amssymb,amsmath,amsthm,latexsym,mathrsfs,amsfonts,dsfont}
\usepackage{color}
\usepackage{url}
%-----accent
\usepackage[latin1]{inputenc} %écrire directement les accents
\usepackage[T1]{fontenc}
% ------------------------------------------------------------
\usepackage{geometry}
\geometry{left=2cm,right=2cm,top=2cm,bottom=2cm}
% ------------------------------------------------------------
\newtheorem{theorem}{Theorem}[section]
\newtheorem{definition}{Definition}[section]
\newtheorem{definitions}{Definitions}[section]
\newtheorem{notation}{Notation}[section]
\newtheorem{corollary}{Corollary}[section]
\newtheorem{proposition}{Proposition}[section]
\newtheorem{lemma}{Lemma}[section]
\newtheorem{remark}{Remark}[section]
\newtheorem{example}{Example}[section]
\numberwithin{equation}{section}
\begin{document}
$\displaystyle\lim_{n\longrightarrow\infty}\langle {\bf T} x_n\; |\;x_n\rangle_A=(\frac{1+i}{2},0,0)$
\end{document}


When I compilate I get

I want to decrease the size of the number (1+i)/2.

Thank you!

You can use \tfrac, though an inline fraction may be better:

\documentclass[12pt,a4paper]{article}

\usepackage{amsmath}

\begin{document}

\begin{equation*}
\lim_{n\to\infty}\langle \mathbf{T} x_n\mid
x_n\rangle_A=(\tfrac{1+i}{2},0,0) = ((1+i)/2,0,0)
\end{equation*}

\end{document}


I have remove irrelevant packages and improved the coding. Note in particular,

• \to instead of \longrightarrow
• \mathbf{T} instead of {\bf T}
• \mid instead of \;|\;
• tank you very much for your help. What are the necessary packages for mathematical papers? I use the following: \usepackage{amssymb,amsmath,amsthm,latexsym,mathrsfs,amsfonts,dsfont} – Student Dec 23 '17 at 10:14
• @Student That is a reasonable selection of packages, but it depends exactly what type of mathematics constructs you need - look up their documentation either on ctan.org or via texdoc ... to see what they do. Also remember the mathtools package that extends amsmath. – Andrew Swann Dec 23 '17 at 11:01
• ... which can be loaded in the place of amsmath, since it loads it. – Bernard Dec 23 '17 at 11:18
• @AndrewSwann Thanks you. I mean what are the necessary mathematical packages for a standard mathematical papers? – Student Dec 23 '17 at 11:30
• @Student There is no fixed standard list of such packages - mathematicians keep inventing new notation... – Andrew Swann Dec 23 '17 at 12:23

Some improvements and suggestions: loading mathtools and xparse, one can define an \innerp command, which displays an inner product typeset in a ‘natural’ way: both arguments are grouped and separated by a comma. The delimiters can be adjusted automatically to the contents with the \innerp* command, or manually with an optional argument: \big,\Big,\bigg or \Bigg.

In addition, I loaded the nccmath package, which defines medium-sized commands (~ 80% of \displaystyle), among which \mfrac, often looking better than \tfrac:

\documentclass[12pt,a4paper]{article}
\usepackage{xparse}
\usepackage{mathtools, nccmath}

\DeclarePairedDelimiterX{\innerp}[1]{\langle}{\rangle}{\innpargs{#1}}
\NewDocumentCommand{\innpargs}{ >{\SplitArgument{1}{,}}m }
{\innpargsaux#1}
\NewDocumentCommand{\innpargsaux}{ m m }
{#1\,\delimsize\vert\,\mathopen{}#2}%\;\delimsize\vert\;

\begin{document}

\begin{equation*}
\lim_{n\to\infty} \innerp[\big]{\mathbf{T}x_n, x_n}=\Bigl(\mfrac{1 + i}{2},0,0\Bigr)=\Bigl(\mfrac{1}{2}(1 + i),0,0\Bigr)
\end{equation*}

\end{document}