Formula_13127

\[\left(\frac{1}{x+i 0} \frac{1}{x+i 0}, \varphi\right)=\left(\frac{1}{(x+i 0)^{2}}, \varphi\right)=\lim _{\varepsilon \rightarrow+0} \int \frac{\varphi(x) d x}{(x+i \varepsilon)^{2}}, \quad \varphi \in D\left(\mathbb{R}^{1}\right) .\]