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\author{Jelani Nelson}
\title{CS 229r Problem Set 1 -- Solutions}

\begin{document}

\maketitle

Here is a theorem with proof.

\begin{theorem}
The square root of $2$ is irrational.
\end{theorem}
\begin{proof}
For the sake of contradiction suppose $\sqrt{2}$ is rational. Write $\sqrt{2} = a/b$ with $a,b$ positive integers with gcd $1$. Then $2 = a^2/b^2$, so $a = 2k$ is even. Then $2 = 4k^2/b^2$ so that $b = 2k^2$, implying $b$ is even. This contradicts that $a,b$ have gcd $1$.
\end{proof}

Some random facts in a list:

\begin{itemize*}
\item Compared with the ``itemize'' environment in \LaTeX, itemize$^*$ has smaller separation between bullet points.
\item The $n$th Catalan number is $C_n \eqdef \frac{1}{n+1} \binom{2n}{n}$.
\item If $\pi(x)$ is the number of primes less than or equal to $x$, then
$$\lim_{x\rightarrow\infty} \frac{\pi(x)}{x/\ln(x)} = 1 . $$
\item $$ \sum_{\substack{1\le i\le 2n\\i\ \mathrm{even}}} i = \frac{2n(n+1)}2 .$$
\end{itemize*}

Have fun on your problem sets.

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