How 'Sine' Got Its Name From a Sanskrit Bow-String
If you have ever opened a trigonometry textbook, you have stared at the word sine without realizing it had crossed three civilizations and survived a translation accident to get to you. The function we use today to describe the ratio of a triangle's opposite side to its hypotenuse is named, somewhat absurdly, after a Latin word meaning bay or fold of a garment . The path from a Sanskrit bow-string to the English word sine is a 1,500-year story about scholars copying each other's notes and getting one word wrong. The Sanskrit origin: jya, the bow-string The story starts with the 5th-century mathematician Aryabhata, who in 499 CE compiled the Aryabhatiya . In it, he tabulated the lengths of half-chords inside a circle for a given arc. The technical Sanskrit term for this half-chord was ardha-jya (अर्धज्या), literally half bow-string . The word jya (ज्या) means bow-string, and the geometric image is direct: a chord cutting across a circle looks like the strung cord of a b...
