Hadamard finite part e principal value

Formula di Plemely-Sochotzki

$$\lim _{\epsilon \to 0}{\frac {1}{x\pm i\epsilon }}=P\left({\frac {1}{x}}\right)\mp i\pi \delta (x)$$

$$\lim _{\epsilon \to 0}{\frac {1}{x\pm i\epsilon }}=P\left({\frac {1}{x}}\right)\mp i\pi \delta (x)$$