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Cosine
(noun)

A mathematical function used in trigonometry to describe the relationship between the angles and sides of a right triangle.

### Origin:

The word 'cosine' is derived from the latin word 'cosinus' which is a transliteration of the greek word 'kosinos' meaning 'complement'. in mathematics, the term was first used by the scottish mathematician john napier in the early 17th century.

### Examples:

- The cosine of an angle is equal to the ratio of the adjacent side to the hypotenuse.
- In a unit circle, the cosine of an angle is equal to the x-coordinate of the point on the circumference.
- The cosine function is periodic and has a range of -1 to 1.
- The cosine similarity is often used in natural language processing to compare the similarity of two documents.
- The cosine of the complement of an angle is equal to the sine of the angle itself.