I've just started using Mathematica and I'm still trying to get used to how things are properly done with it. I tried to do a calculation (this one: https://www.physicsforums.com/threads/lagrangian-of-a-driven-pendulum-landau-problem.965714/) and I had to neglect some terms in an expression. Is there any tool in Mathematica where I can specify some condition like 'term has explicit time dependence' and it automatically throws out the terms that meet that condition? Or how is this done with these calculations? For now, I just subtracted it from the variable manually but I suppose there's some more elegant way of doing this. EDIT: As the problem above has been solved I must add that I actually don't need to neglect terms there, because they fall out on their own, but I'm still curious if there are such tools in Mathematica.