Editing Group delay and phase delay (section)

=== Polynomial ratio ===
A polynomial ratio of the form <math>P2(S) = P_{num}(S)/P_{den}(S)</math>, such as that typically found in the definition of [[filter design]]s, may have the group delay determined by taking advantage of the phase relation, <math>\phi(P1/P2) = \phi(P1) - \phi(P2)</math>.

<math>\text{Group Delay} = gd(P2) = gd(P2_{num}) - gd(P2_{den}) sec</math>