# Lagrangian of the EM field -- question

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## Main Question or Discussion Point

The EM Lagrangian is
$$\mathcal{L} = -\frac{1}{2}[(\partial_\mu A_\nu)(\partial^\mu A^\nu) - (\partial_\mu A_\nu)(\partial^\nu A^\mu)]$$

In the QFT notes from Tong the EM Lagrangian is written in the form
$$\mathcal{L} = -\frac{1}{2}[(\partial_\mu A_\nu)(\partial^\mu A^\nu) - (\partial_\mu A^\mu)^2]$$

I don't see how did he get $(\partial_\mu A^\mu)^2$ term? Thanks :)

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Orodruin
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