# latex testing

$\begin{tabular}{c c c} \hline X$_{1}$& cell2 & cell3 \ \hline cell4 & cell5 & cell6 \ cell4 & cell5 & cell6 \ \hline \end{tabular}$

$X_{1i}$, $X_{2i}$, and $X_{3i}$ are three different variables measured across a sample of individuals

$[ a_1^2 + a_2^2 = a_3^2 ]$