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In mathematics, Kachurovskii's theorem is a theorem relating the convexity of a function on a Banach space to the monotonicity of its Fréchet derivative. ==Statement of the theorem== Let ''K'' be a convex subset of a Banach space ''V'' and let ''f'' : ''K'' → R ∪ be an extended real-valued function that is Fréchet differentiable with derivative d''f''(''x'') : ''V'' → R at each point ''x'' in ''K''. (In fact, d''f''(''x'') is an element of the continuous dual space ''V''∗.) Then the following are equivalent: * ''f'' is a convex function; * for all ''x'' and ''y'' in ''K'', :: * d''f'' is an (increasing) monotone operator, i.e., for all ''x'' and ''y'' in ''K'', :: 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Kachurovskii's theorem」の詳細全文を読む スポンサード リンク
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