\documentclass[]{article}
\usepackage{amsmath}
\title{CS243 Lab}
\author{Weilin}


\begin{document}

\maketitle



\section{Math Symbols}
\begin{enumerate}
\item Now, let's print some inline math symbol: $\beta$ and $\alpha$
\item Then, display math: \[ \phi \equiv p \to q \] \[(p \land q) \lor \lnot r \]
\item A list of math symbols: 
\begin{enumerate}
 \item Greek Letters: $\alpha , \beta , \pi, \Sigma, \Omega$
 \item connectives: $\land, \lor, \lnot, \to,\leftrightarrow, \oplus$
\end{enumerate}


\end{enumerate}

\section{Math formulae alignment}
Equation alignment:
\begin{align*}
  n &= \sum_{i=1}^k n_i + 1\\
  &= \sum_{i=1}^k (e_i + 1) +1\\
  &= \sum_{i=1}^k e_i + k + 1\\
  &= e + 1.
\end{align*}

Another alignment:
\begin{align}
  n &= \sum_{i=1}^k n_i + 1\\
  &= \sum_{i=1}^k (e_i + 1) +1\\
  &= \sum_{i=1}^k e_i + k + 1\\
  &= e + 1.
\end{align}

\end{document}
