One day at tifr-h, a boy came inside [somehow]

why don't you teach me physics
the boy asked

OK. I said.

$\epsilon_{\mu \nu} = \begin{pmatrix} 0 & 1 \\ -1 & 0 \end{pmatrix}$


$\epsilon_{\mu \nu} \epsilon^{\nu \rho} = g^{\rho}_{ \ \mu}  $