Ci dev’essere qualcosa che disturba, perché in un esempio minimo
compilabile tutto fila liscio…Invece qui no:
`\documentclass[a4paper,titlepage,fleqn]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[italian]{babel}
\usepackage[margin=2.8cm]{geometry}
\setlength{\parindent}{0pt}
\usepackage{pig}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{tabularx}
\usepackage{multicol} % per righe multicolonna
\usepackage{multirow} % per colonne multiriga
\usepackage{booktabs} % per toprule midrule e bottomrule
\usepackage{ragged2e} % per sillabare nelle tabelle
\newcommand{\verticale}[2][c]{%
\raisebox{1sp}{\smash{\rotatebox[origin=rc]{90}{%
\begin{tabular}{@{}#1@{}}#2\end{tabular}}}}}
\usepackage{enumitem}
\setlist{noitemsep}
\usepackage{fancyhdr}
\pagestyle{fancy}
\setlength{\headheight}{14.5pt}
\fancyhf{}
\fancyhead[LE]{\thepage \hfill III D — Documento del 15 maggio }
\fancyhead[RO]{III D — Documento del 15 maggio \hfill \thepage}
\frenchspacing
\newenvironment{lista}{\setlength{\parindent}{0pt}\setlength{\parskip}%
{1ex plus 0.5ex minus 0.2ex}}
\renewcommand{\sin}{\operatorname{sen}}
\renewcommand{\tan}{\operatorname{tg}}
\renewcommand{\cot}{\operatorname{cotg}}
\begin{document}
\[
\sin^2\Bigl({\alpha+\frac{\pi}{6}}\Bigl)-\cos^2\Bigl({\alpha+\frac{\pi}{6}}
\Bigl) =\frac{-\cos2a}{2}
\]
\[
\sin\alpha-\tan\frac{\alpha}{2}=2\sin^2\frac{\alpha}{2}\cdot\frac{1}{
\tan\alpha}
\]
\end{document}`
M.