ELI5: Explain Like I'm 5

Fundamental lemma of the calculus of variations

The Fundamental Lemma of the Calculus of Variations is a way to look for the best possible answers to a problem. It helps us to find the best situation for a given situation.

Think of it like this: You have a problem and you want to find the best answer. With the Fundamental Lemma of the Calculus of Variations, you can do just that! You can work out all the possibilities and then find the best one. It's like having a special calculator that can tell you what the best answer should be.