cosine
|co-sine|
🇺🇸
/ˈkoʊ.saɪn/
🇬🇧
/ˈkəʊ.saɪn/
ratio of adjacent side to hypotenuse (sine of complement)
Etymology
'cosine' originates from Neo-Latin, specifically the word 'cosinus', where the prefix 'co-' meant 'complementary (to)' and 'sinus' meant 'sine'.
'cosinus' appeared in Medieval/Neo-Latin and then in French before becoming the modern English word 'cosine'. The element 'sine' itself traces back through Latin 'sinus' to Arabic 'jayb' and ultimately to Sanskrit 'jya'.
Initially, it referred to the 'sine of the complementary angle'; over time it came to denote the standalone trigonometric function and the ratio adjacent/hypotenuse.
Meanings by Part of Speech
Noun 1
in trigonometry, the trigonometric function cos(x); for an angle in a right triangle, the ratio of the length of the adjacent side to the hypotenuse.
The cosine of 60° is 1/2.
Synonyms
Noun 2
the numerical value produced by the cosine function for a given angle (e.g., cos(π/3) = 1/2).
Compute the cosine of the angle to use in the formula.
Synonyms
Last updated: 2026/01/06 05:25