the-honk/maths/style.cls

\LoadClass[17pt]{extarticle}
\pagenumbering{gobble}

\usepackage{geometry}
\geometry{a4paper, portrait, margin=1in}

\newcommand{\euler}{\begin{gather*}
	\text{By Euler's formula:} \\
	e^{i\theta} = cos(\theta) + i\sin(\theta) \\
	e^{-i\theta} = cos(\theta) - i\sin(\theta)
\end{gather*}}