Talk:First variation

The first variation, with the definition given here, is equivalent to the directional derivative. --Kaba3 (talk) 15:03, 24 November 2012 (UTC)[reply]

2nd variation

is it necessary to verify the second variation? Jackzhp (talk) 02:36, 21 January 2009 (UTC)[reply]

If you want to know if a functional is minimized by a given function, then a necessary condition is that the second variation is positive when evaluated at that function. 66.57.5.47 (talk) 06:28, 18 April 2009 (UTC)[reply]

Merge with article about functional derivative

I'm not extremely well versed in this area of mathematics, but isn't this article about essentially the same thing as the article Functional derivative? — Preceding unsigned comment added by 217.10.109.18 (talk) 18:38, 9 March 2018 (UTC)[reply]