preamble.tex

\usepackage{amssymb}
\usepackage{xfrac}
% \usepackage{mdframed}

\usepackage[framemethod=TikZ]{mdframed} % noteboxes, boxes, etc.

\newcounter{definition}
\newenvironment{defin}[1][]{%
\stepcounter{definition}%
\ifstrempty{#1}%
{\mdfsetup{%
        frametitle={%
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=white]
            {\strut Definición};}}
            % {\strut Definición~\thedefinition};}}
            
}%
{\mdfsetup{%
        frametitle={%
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=white]
            {\strut Definición:~#1};}}%
            % {\strut Definición~\thedefinition:~#1};}}%
}%
\mdfsetup{innertopmargin=1pt,linecolor=black!60,%
    linewidth=1pt,topline=true,
    frametitleaboveskip=\dimexpr-\ht\strutbox\relax,}
\begin{mdframed}[]\relax%
}{\end{mdframed}}

\newcounter{theorem}
\newenvironment{theo}[1][]{%
\stepcounter{theorem}%
\ifstrempty{#1}%
{\mdfsetup{%
        frametitle={%
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=white]
            {\strut Teorema};}}
            % {\strut Teorema~\thetheorem};}}
}%
{\mdfsetup{%
        frametitle={%
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=white]
            {\strut Teorema~(#1)};}}%
            % {\strut Teorema~\thetheorem:~#1};}}%
}%
\mdfsetup{innertopmargin=1pt,linecolor=black!60,%
    linewidth=1pt,topline=true,
    frametitleaboveskip=\dimexpr-\ht\strutbox\relax,}
\begin{mdframed}[]\relax%
}{\end{mdframed}}

% \newmdtheoremenv{theo}{Teorema}
% \newmdtheoremenv{defin}{Definición}

% \usepackage{amsmath}
\usepackage{booktabs}
\ifxetex
  \usepackage{polyglossia}
  \setmainlanguage{spanish}
  % Tabla en lugar de cuadro
  \gappto\captionsspanish{\renewcommand{\tablename}{Tabla}  
          \renewcommand{\listtablename}{Índice de tablas}}
\else
  \usepackage[spanish,es-tabla]{babel}
\fi
\usepackage{fancyhdr}
\pagestyle{fancy}
\renewcommand\subsectionmark[1]{}
\renewcommand\sectionmark[1]{}

\renewcommand{\arraystretch}{1.15}
\setlength{\headheight}{15pt}

% \renewcommand\frac[2]{{\scriptstyle\dfrac{#1}{#2}}}

% \usepackage[skins]{tcolorbox}
% 
% \newtcolorbox{myframe}[2][]{%
%   enhanced,colback=white,colframe=black,coltitle=black,
%   sharp corners,boxrule=0.4pt,
%   fonttitle=\itshape,
%   attach boxed title to top left={yshift=-0.3\baselineskip-0.4pt,xshift=2mm},
%   boxed title style={tile,size=minimal,left=0.5mm,right=0.5mm,
%     colback=white,before upper=\strut},
%   title=#2,#1
% }
% 
% \newcommand{\ejemplo}{1}{\begin{myframe}{__Ejemplo__}
% #1
% \end{myframe}
% }