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Abouabdillah's theorem refers to two distinct theorems in mathematics, proven by Moroccan mathematician Driss Abouabdillah: one in geometry and one in number theory. ==Geometry== In geometry, similarities of a Euclidean space preserve circles and spheres. Conversely, Abouabdillah's theorem states that every injective or surjective transformation of a Euclidean space that preserves circles or spheres is a similarity. More precisely: Theorem. Let be a Euclidean affine space of dimension at least 2. Then: 1. Every surjective mapping that transforms any four concyclic points into four concyclic points is a similarity. 2. Every injective mapping that transforms any circle into a circle is a similarity. 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「Abouabdillah's theorem」の詳細全文を読む スポンサード リンク
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