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English definition of “cosine”

cosine

noun [C] uk   /ˈkəʊ.saɪn/ us    /ˈkoʊ-/ (written abbreviation cos) specialized
(in a triangle that has one angle of 90°) the ratio of the length of the side next to an angle less than 90°, divided by the length of the hypotenuse (= the side opposite the 90° angle)
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Parts of geometrical shapes
(Definition of cosine from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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