Let be a functional S so [tex] \delta S =0 [/tex] give the Euler-Lagrange equation where:(adsbygoogle = window.adsbygoogle || []).push({});

[tex] S= \int_{a}^{b}dtL(q,\dot q, t) [/tex]

My question is ..How the "second variation" [tex] \delta ( \delta S )=0= \delta ^{2} S [/tex] defined??.. in order we could decide if a function q=q(t) is either a maximum or a minimum point of function space.. thanks.

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# Second variation

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