Py ‧ thag ‧ o ‧ ras /paɪˈθæɡ ə rəs $ pə-/ BrE AmE
(?582-?507BC) a Greek ↑ philosopher and ↑ mathematician , known for Pythagoras' Theorem, a way of calculating the length of one side of a ↑ triangle which has one angle of 90°, when you already know the length of the other two sides