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Contents Dark Mode Prev Up Next \(\DeclareMathOperator{\sgn}{sgn}
\DeclareMathOperator{\Inn}{Inn}
\DeclareMathOperator{\lcm}{lcm}
\DeclareMathOperator{\Aut}{Aut}
\DeclareMathOperator{\Perm}{Perm}
\DeclareMathOperator{\Stab}{Stab}
\DeclareMathOperator{\Orb}{Orb}
\DeclareMathOperator{\Rot}{Rot}
\DeclareMathOperator{\re}{Re}
\DeclareMathOperator{\im}{Im}
\DeclareMathOperator{\img}{image}
\DeclareMathOperator{\conj}{conj}
\DeclareMathOperator{\Id}{Id}
\def\expi{E}
\def\wrap{W}
\newcommand{\C}{\mathbb{C}}
\newcommand{\Quat}{\mathbb{H}}
\newcommand{\extC}{\hat{\C}}
\newcommand{\R}{\mathbb{R}}
\newcommand{\extR}{\hat{\R}}
\newcommand{\F}{\mathbb{F}}
\newcommand{\extF}{\hat{\F}}
\newcommand{\Z}{\mathbb{Z}}
\newcommand{\Proj}{\mathbb{P}}
\newcommand{\Q}{\mathbb{Q}}
\newcommand{\B}{\mathbb{B}}
\newcommand{\M}{{\rm MOB}}
\newcommand{\E}{{\rm EUC}}
\renewcommand{\H}{{\rm HYP}}
\newcommand{\HU}{\rm HYP_{\U}}
\renewcommand{\S}{{\rm ELL}}
\newcommand{\D}{\mathbb{D}}
\newcommand{\closedD}{\hat{\D}}
\newcommand{\U}{\mathbb{U}}
\newcommand{\spacer}{\rule[0cm]{0cm}{0cm}}
\newcommand{\MOD}{\mathbin{\text{MOD}}}
\newcommand{\twotwo}[4]{\left[ \begin{array}{cc} #1 \amp #2 \\
#3 \amp #4 \end{array} \right]}
\let\oldsection\section
\renewcommand{\section}{\clearpage\oldsection}
\newcommand{\lt}{<}
\newcommand{\gt}{>}
\newcommand{\amp}{&}
\definecolor{fillinmathshade}{gray}{0.9}
\newcommand{\fillinmath}[1]{\mathchoice{\colorbox{fillinmathshade}{$\displaystyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\textstyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\scriptstyle \phantom{\,#1\,}$}}{\colorbox{fillinmathshade}{$\scriptscriptstyle\phantom{\,#1\,}$}}}
\)
Chapter 2 Sets
Characteristic functions.
In the same way that logical expressions logical identities are mirrored in Boolean algebra, expressions involving sets and set identites are mirrored in the algebra of characteristic functions.
