Last time you guys were able to see through the (to me) somewhat cluttered use of integrals and differentiation (I'm still very grateful for your amazing help). This time my question is similar. I'm currently trying to understand the following derivation of Lagrange's equations from Landau and Lifshi-tz' amazing first volume on mechanics:
The function for the action
What is meant by the sentence at (1)? Which calculations aren't shown here?
How is this translated to affect the variation at (2)?
How did we get to (3)?
Edit: Having studied this further the last couple of days, I've realized what a stupid question it was. I'm gonna read up on calculus of variations and understand this fully!
Last edited by Hixy (2011-10-18 10:39:17)
Hi I have been searching for answers to these very questions and, since you seem to have figured them out, would you mind explaining the reasoning behind (1)? I get the rest of the derivation but the expansion in powers of del(q) and del(dq/dt) is still not making sense to me! Thank you so much.