third.tex

\documentclass[a4paper,11pt]{article}
\usepackage{amsmath}
\title{Let's do some maths!}
\author{Wacky professor}
\date{\today}
\begin{document}
\maketitle
So we're in the middle of talking when suddenly, $\forall x \in X$, and the room went silent. You could hear a pin drop, until the hitherto unnoticed figure in the corner blurted out:
\begin{equation}
e^{i\theta}= \cos\theta + i\sin\theta
\end{equation}
Without a pause, he proceeded to recite:
\begin{equation}
\sum_{n=0}^{\infty}\frac{f^{(n)}(a)}{n!}(x-a)^{n}
\end{equation}
\end{document}