Mathematics!
Add $a$ squared to $b$ squared to get $c$ squared, i.e.,
$a^2 + b^2 = c^2$. |
Add $a$ squared to $b$ squared to get $c$ squared, i.e., $$ a^2 + b^2 = c^2, $$ in (Plain) TeX. |
Add $a$ squared to $b$ squared to get $c$ squared, i.e.,
\begin{displaymath}
a^2 + b^2 = c^2,
\end{displaymath}
or \[ \], or
\begin{equation}
a^2 + b^2 = c^2.
\end{equation}
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Sometimes we have groups of equations that we want lined up nicely:
\begin{eqnarray}
\epsilon \frac {{\rm d}^2\psi} {{\rm d}t^2} & = & - \psi \\
q \frac{\partial p} {\partial t}
& = & - \nabla . J_{p} - qR
\end{eqnarray}
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\begin{eqnarray}
& & \epsilon \frac {{\rm d}^2\psi} {{\rm d}t^2} = - \psi \\
& & q \frac{\partial p} {\partial t}
= - \nabla . J_{p} - qR
\end{eqnarray}
|
\begin{displaymath}
\mathbf{X} = \left(
\begin{array}{ccc}
x_{11} & x_{12} & \ldots \\
x_{21} & x_{22} & \ldots \\
\vdots & \vdots & \ddots
\end{array}
\right)
\end{displaymath}
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\begin{equation}
\label{eq:myeq}
\epsilon > 0
\end{equation}
From equation (\ref{eq:myeq}) we see that\ldots
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