Table of displayed formulae

Perhaps the array packages offers a partial solution:

\documentclass{article}
\usepackage{array}
\setlength{\extrarowheight}{8pt}
\begin{document}
$\begin{array}{>{\displaystyle}c|>{\displaystyle}c>{\displaystyle}c|>{\displaystyle}c}
\frac{x}{y}&z&\frac{x}{y}&\frac{x}{y}\\[1em]\hline
\frac{x}{y}&\frac{x}{y}&z&\frac{x}{y}\\[1em]\hline
\end{array}$
\end{document}

\documentclass[11pt]{scrartcl}
\usepackage{array}
\newcolumntype{C}{>{$\displaystyle} c <{$}}
\begin{document} 

\def\arraystretch{2}
\begin {tabular}{| C | C |}\hline
\frac1{1+x^2} & \mathrm{atan}(x)+C \\\hline
\sqrt{x^2+h}  & \ln\left(x+\sqrt{x^2+h}\right)+C\\\hline
\end{tabular}
\end{document}

For this kind of table, it's also possible to use the next code. I keep \tvito get the same height for each row and I use p{#1} to control the width of each column.

\documentclass[11pt]{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage{fourier}
\usepackage{array} 
\usepackage{booktabs,amsmath}      
\begin{document}

\newcommand{\tvi}{\vrule height 17pt depth15pt width 0pt} 

\newcolumntype{x}[1]{>{\hfil$\displaystyle} p{#1} <{$\hfil}} 

\begin{tabular}{x{4cm} x{4cm} }\\
\text{\bfseries{Fonctions}}   & \text{\bfseries{ Primitives}}       \\ \midrule
\tvi   \frac{ 1} {1+x^2 }     & \mathrm{ arctan}\,(x)+C             \\ \midrule 
\tvi   \frac{1}{\sqrt{x^2+h}} & \log\bigl(x+\sqrt{x^2+h}\,\bigr)+C  \\                                                                         
\end{tabular}

\end{document} 

Without an environment but with an old method : TeX

\def\hfq{\hfill\quad}
\def\cc#1{\hfq#1\hfq}
\def\tvi{\vrule height 12pt depth 5pt width 0pt}
\def\tv{\tvi\vrule}

\vbox{\offinterlineskip
\halign {\tv#&&\cc{$\displaystyle#$}&\tv#\cr
\noalign{\hrule}
&\omit\cc{\bf Fonctions}&&\omit\cc{\bf Primitives}&\cr
\noalign{\hrule}
height 17pt depth15pt&{1\over 1+x^2}&&{\rm Arctg}\,(x)+C&\cr
\noalign{\hrule}
height 17pt depth17pt&{1\over\displaystyle\sqrt{x^2+h}}&&
\log\bigl(x+\sqrt{x^2+h}\,\bigr)+C&\cr
\noalign{\hrule}}}