Add last lecture notes (Yes there's some missing)
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week3/27-01-2022/27-01-2022.tex
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week3/27-01-2022/27-01-2022.tex
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% File: 27-01-2022.tex
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% Created: 12:36:49 Thu, 27 Jan 2022 EST
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% Last Change: 12:36:49 Thu, 27 Jan 2022 EST
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%
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\documentclass[letterpaper]{article}
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\usepackage{amsmath}
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\usepackage{graphicx}
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\usepackage{cancel}
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\usepackage{amssymb}
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\usepackage{listings}
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\usepackage[shortlabels]{enumitem}
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\usepackage{soul}
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%\usepackage[smartEllipses,hashEnumerators,hybrid]{markdown}
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%\usepackage{minted}
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\usepackage{geometry}
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\usepackage{dirtytalk}
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\usepackage{lplfitch}
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\geometry{portrait, margin=1in}
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%\begin{minted}[linenos,bgcolor=LightGray]{[language]}
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\date{01/27/2022}
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\title{%
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Starting Proofs\\
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\large MATH--190--01: Discrete Mathematics for Computing}
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\author{Blizzard MacDougall}
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\begin{document}
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\maketitle
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\pagenumbering{arabic}
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We have the following rules so far:
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\begin{itemize}
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\item $A=A$
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\item $A=B\to B=A$
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\item $[(A=B)\land (B=C)] \to (A=C)$
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\item $\mathbb{Z}$ is all whole integers.
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\item Integers are closed under $+,\ -,\ \times$ but not $\div$
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\end{itemize}
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There are two ways to prove statements.
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\begin{itemize}
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\item \textit{Constructive proofs} - Find the thing, or show how to.
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\begin{itemize}
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\item Perfect numbers exist (There are numbers which is the sum of its proper divisors.) 6
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\item Suppose $r,s\in \mathbb{Z}$. Prove that there exists an integer $k$ such that $24r+4s=2k$
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\end{itemize}
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\item \textit{Nonconstructive proofs} - Show that it has to exist, but don't say how or what it is.
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\begin{itemize}
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\item Given any set of 2 consecutive integers, one of them is even.
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\item Roth's theorem. If $\alpha$ is any algebraic irrational number, then there are
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only finitely many rational numbers such that
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$\left|\alpha - \frac{p}{q}\right| <\frac{1}{q^{2+\epsilon}}$
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\end{itemize}
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\end{itemize}
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The easiest way to disprove a universal statement is that you have to show the inverse.
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That is, you have to find one instance where it isn't true.
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\emph{Proving} a universal statement is significantly harder. If $\mathbb{D}$ is finite,
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the method of exhaustion is easiest. However, the best technique is to generalize from a generic
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parameter. That is, pick a general element, then show that it satisfies the statement.
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Generally $x$ is reserved for a real number, and $n$ is reserved for integer use.
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To prove a $\forall x\in \mathbb{D}$:
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\begin{enumerate}
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\item Express the statement to be proved in the form:
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\begin{equation}
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\forall x\in \mathbb{D} P(x)\to Q(x)
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\end{equation}
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\item "Suppose $x\in \mathbb{D} \land P(x)$"
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\item Prove $Q(x)=\top$
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\end{enumerate}
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Example proof:\\
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For all integers $m$ and $n$, if $m$ and $n$ are odd, then $m\times n$ is odd.\\
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Proof: Let $m$ and $n$ be odd integers.\\
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Since $m$ is odd, there is an integer $r$ such that $m=2r+1$.\\
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Similarly, there is an integer $s$ such that $n=2s+1$.\\
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Since $m\times n = (2r+1)(2s+1) = 4rs+2r+2s+1 = 2(2rs+r+s) + 1$\\
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Let $k=2rs+r+s$. Note that $k$ is an integer.\\
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$\therefore m\times n=2k+1$, so $m\times n$ is odd. QED
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\end{document}
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week4/03-02-2022/03-02-2022.tex
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week4/03-02-2022/03-02-2022.tex
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% File: 20-01-2022.tex
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% Created: 12:28:35 Thu, 20 Jan 2022 EST
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% Last Change: 12:28:35 Thu, 20 Jan 2022 EST
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%
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\documentclass[letterpaper]{article}
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\usepackage{amsmath}
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\usepackage{graphicx}
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\usepackage{cancel}
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\usepackage{amssymb}
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\usepackage{listings}
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\usepackage[shortlabels]{enumitem}
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\usepackage{soul}
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%\usepackage[smartEllipses,hashEnumerators,hybrid]{markdown}
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\usepackage{geometry}
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\usepackage{dirtytalk}
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\usepackage{lplfitch}
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\geometry{portrait, margin=1in}
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%\begin{minted}[linenos,bgcolor=LightGray]{[language]}
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\date{01/20/2022}
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\title{%
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LectureName\\
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\large MATH--190--01 : Discrete Mathematics for Computing}
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\author{Blizzard MacDougall}
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\begin{document}
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\maketitle
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\pagenumbering{arabic}
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\end{document}
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