\newcommand{\eqn}{\nabla \times \mathbf{E} = - \frac{\partial \mathbf{B}}{\partial t}}

Turned into a proof environment.

$$\eqn$$

First class is picked and converted into a LaTeX environment.

$$\eqn$$

Shouldn't be converted into LaTeX environments. Since LaTeX is false.

Also shouldn't be converted into LaTeX environments. Since LaTeX is not present.

