missing $inserted error for equation I get the missing$ inserted error for the following code:

$$C =  \frac{2}{\omega^2N^2\mu\pia}$$


I have tried out different changes based on Googling for this error, but nothing seems to help. Any suggestions would be appreciated.

• Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. – user11232 Nov 2 '14 at 3:20

1. Don't put $ inside the equation environment. You can't use math mode (ie, $...\$ inside math mode (ie, $$...$$)
2. Don't leave empty lines inside the equation environment.
3. \pia should be \pi a. Note the space.
\documentclass{article}
$$C = \frac{2}{\omega²N²μ\pi a}$$