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\begin{center} \bf \large Example 0
\end{center}

\emph{Inline math} The area $A$ of a circle of radius $r$ is $A=\pi r^2$.

Since to write this (see the .tex  file) we used a dollar sign, how do
you get a dollar sign? Use \$, as: peaches cost \$1.27 a pound.
\medskip

\emph{Display math} (unnumbered equatons):
\[
\int_0^\infty e^{-t^2}\,dt = \frac{\sqrt{\pi}}{2}.
\]

\emph{Display math} (numbered equatons):
\begin{equation}\label{bell-curve}
\int_0^\infty e^{-t^2}\,dt = \frac{\sqrt{\pi}}{2}.
\end{equation}
In the study of probability, this equation \eqref{bell-curve}
is vital.

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