Translations:Dictionary:Causality/47/en

$\int _{-\infty }^{\infty }f(t)e^{i\omega t}\;dt=F(\omega )={\frac {1}{\pi }}{\mbox{PV}}\int _{-\infty }^{\infty }{\frac {F_{I}(\Omega )}{(\Omega -\omega )}}\;d\Omega +i{\frac {-1}{\pi }}{\mbox{PV}}\int _{-\infty }^{\infty }{\frac {F_{R}(\Omega )}{(\Omega -\omega )}}\;d\Omega .$