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In mathematics, Pythagorean addition is the following binary operation on the real numbers: : The name recalls the Pythagorean theorem, which states that the length of the hypotenuse of a right triangle is where ''a'' and ''b'' are the lengths of the other sides. This operation provides a simple notation and terminology when the summands are complicated; for example, the energy-momentum relation in physics becomes : ==Properties== The operation ⊕ is associative and commutative, and :. This is enough to form the real numbers into a commutative semigroup. However, ⊕ is not a group operation for the following reasons. The only element which could potentially act as an identity element is 0, since an identity ''e'' must satisfy ''e''⊕''e'' = ''e''. This yields the equation , but if ''e'' is nonzero that implies , so ''e'' could only be zero. Unfortunately 0 does not work as an identity element after all, since 0⊕(−1) = 1. This does indicate, however, that if the operation ⊕ is restricted to nonnegative real numbers, then 0 ''does'' act as an identity. Consequently the operation ⊕ acting on the nonnegative real numbers forms a commutative monoid. 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「Pythagorean addition」の詳細全文を読む スポンサード リンク
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