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)

2nd variation

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

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)

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)