I am reviewing the first chapter of my classical mechanics book (Fetter & Walecka), and in the very first section he uses the term "dynamical trajectory". I have seen this derivation many times, but I just don't understand exactly what that term means.
Here is the page (he goes from 1.7a to 1.7b using this principle)
![]()
Here is the page (he goes from 1.7a to 1.7b using this principle)
