# Sinus

One of the first trigonometric functions was known to us from the school bench **sinus**. The word "sinus" appeared in mathematics far from immediately. This term has its long (from 1 - 2 cc.) and interesting history. The wave-shaped curve, graphically depicting the change in the sine, depending on the angle change, was originally called the "archa-jiva" (half-word) for Indian mathematicians, then the word "archa" was discarded and the sine became simply called "jiva." Arabic translators began to call the sine "jibe". Since in Arabic, short vowels are not designated, the sine was pronounced as "jayb", which literally means "hollow" (sinus). When translating Arabic works into Latin, European translators translated the word "jayb" with the Latin word "sinus" (sine), which has the same meaning. The Austrian mathematician and astronomer Georg von Poyerbach (1423-1461) was one of the first European scholars to apply the sine as a concept; He also compiled a table of sine values every 10 minutes. This work was completed by his pupil Regiomontan. Regiomontan Koenigsberg (1436-1476, real name - Johann Muller) - German astronomer and a mathematician who lived at the turn of the Middle Ages and New Time.

A great contribution to the further development of trigonometry was made by the outstanding French mathematician, astronomer and physicist Gilles Roberval (1602-1675). Roberval was the first to build a sinusoid. It happened in 1634. What is the sin of the angle *x*? This is the ratio of the opposite leg to the hypotenuse: **sinx = a/c**. The sin of a real argument is a periodic continuous and infinitely differentiable real-valued function.