Tugtar Prionsabal an iosghniomhaithe ar an bprionsabal bunusach sa mheicnic go bhfeidhmionn coras meicniuil ionas go n-eirionn a ghniomhu nios lu de reir a cheile go mbaintear iosghniomhu amach.
Diorthaitear cothromoidi Euler-Lagrange on bprionsabal seo. Cas ar leith de is ea prionsabal Fermat maidir le h optaic . Is analog chandamach de suimeail chonair Feynman. [1]