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In complex analysis, a branch of mathematics, the residue at infinity is a residue of a holomorphic function on an annulus having an infinite external radius. The ''infinity'' is a point added to the local space in order to render it compact (in this case it is a one-point compactification). This space noted is isomorphic to the Riemann sphere.〔Michèle AUDIN, ''Analyse Complexe'', cursus notes of the university of Strasbourg (available on the web ), pp. 70–72〕 One can use the residue at infinity to calculate some integrals. ==Definition== Given a holomorphic function ''f'' on an annulus (centered at 0, with inner radius and infinite outer radius), the residue at infinity of the function ''f'' can be defined in terms of the usual residue as follows: : Thus, one can transfer the study of at infinity to the study of at the origin. Note that , we have : 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「Residue at infinity」の詳細全文を読む スポンサード リンク
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