cosine
UK[ˈkəʊsaɪn]US[ˈkoʊsaɪn]
n
(in a right-angled triangle) the ratio of the length of the side adjacent to a given acute angle to the length of the hypotenuse.
n
(in trigonometry) a function of an angle that is the sine of its complement.
Morpheme Breakdown
co
sine
co
together, jointly, in complement.
sine
curve, fold, bay.
Etymology
The word "cosine" is a modern mathematical contraction of the Latin phrase "complementi sinus," meaning "sine of the complement." It was coined in the 17th century by English mathematician Edmund Gunter. The term "sine" itself has a winding history, originating from the Latin "sinus" (a curve, fold, or bay), which was used to translate the Arabic "jayb" (pocket or bosom), a mistranslation of the Sanskrit "jya" (chord). Thus, "cosine" literally encodes the trigonometric identity that the cosine of an angle is the sine of its complementary angle, linking a geometric relationship to its linguistic construction.
Analysis
Structure: co + sine
co: A prefix of Latin origin (from 'com-'), meaning "together, jointly, in complement." In this word, it signifies "complement."
sine: A word of Latin origin (from 'sinus'), meaning "curve, fold, bay." In trigonometry, it was historically used to name the sine function.
Examples
The cosine of 60 degrees is 0.5.
In the graph, the cosine wave starts at its maximum value.
You need to use the inverse cosine function to find that angle.