\documentclass[12pt,letterpaper]{amsart}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{graphicx}
\begin{document}
Here is some stuff, with some $$\int x^2 dx$$ math., and {\bf bold}. Tje rea;s are ${\mathbb R}$.
$$
\begin{aligned}
\label{y_pow}
\sum^{\infty}_{i=1} a_i y^i &=\\
 & 27 \cos{\pi x} \\ 
 before  & after
\end{aligned}
$$

\begin{minipage}{2in}
\centerline{\includegraphics[height=1in]{sin.eps}}
\end{minipage}
\begin{minipage}{4in}
Over there is a graph of the sin.
$$ x^2$$
and stuff

\end{minipage}
\section{Math mode}
An x is different from an $x$.  I want to display an equation.
\[ \frac{x^2 + 5}{x^2 - x + 2} 
stuff stuffy stuff \]
versus $\frac{x^2 + 5}{x^2 - x + 2}$.

versus
\begin{equation} \label{x_pow_ser}
\sum^{\infty}_{i=1} a_i x^i
\end{equation}
This is m ore stu  here is a set $\{x | x>4 \}$.     ggggggads  \\[2in] 
fdgsdfg  adfhdft.

Compare (\ref{x_pow_ser}) with (\ref{y_pow}).
\end{document}