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} |
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} |
\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} |
\begin{equation} \label{eq:myeq} \epsilon > 0 \end{equation} From equation (\ref{eq:myeq}) we see that\ldots |