ah . i jumped directly from lollipop to nougat so I don ' t know what all On Tap had to offer <| sep |> Very little . Not much is actually known about Pythagoras himself . We know that he lived in Greek southern Italy in the 6 th century BCE , and that he established a group of followers whose philosophy impacted later Greek thinkers such as Plato . However , the evidence linking various mathematical discoveries to him and his school is weak . The two mathematical results most often attributed to him are Pythagoras ' s Theorem and the incommensurability of the side and diagonal of a square . Both , however , were likely known in Mesopotamia before Pythagoras , while their earliest proofs appear well after him and sources attributing the results to him are late and unreliable . A fair amount of trigonometry was codified a couple of hundred years after Pythagoras in Euclid ' s Elements , though in a geometric rather than trigonometric fashion . The title ' father of trigonometry ' is usually given to Hipparchus of Nicaea , who lived in the 2 nd century BCE and compiled some of the first trigonometric tables . The modern trigonometric functions sine and cosine , however , actually derive from 6 th century Indian astronomy , via translation to Arabic and then to Latin . Hipparchus and later Ptolemy used the circlebased chord function instead . Postscript One mathematical result more plausibly credited to the Pythagoreans is the relation of musical harmony and physical ratios . Furthermore , Aristotle credits Pythagoreans with the theory that things themselves are numbers , which is interpreted by some as an early claim that mathematics can be used to describe reality .