Question

what is sin, cos, tan etc......

Answer 1

You're going to be really confused by all of these answers, just going to let you know that right now.

Answer 2

trigonometric function, 1590s (in Thomas Fale's "Horologiographia, the Art of Dialling"), from L. sinus "fold in a garment, bend, curve." Used mid-12c. by Gherardo of Cremona in M.L. translation of Arabic geometrical text to render Arabic jiba "chord of an arc, sine" (from Skt. jya "bowstring"), which he confused with jaib "bundle, bosom, fold in a garment."

Answer 3

I'm going to assume you're in Geometry because of your questions, but they can be used to find angles and lengths of triangles, and other things in the future, but mostly triangles.