#Pythagoras -site:classicalliberalarts.com -site:www.mathopenref.com -site:www.britannica.com -site:www.mathsisfun.com -site:mathshistory.st-andrews.ac.uk -site:en.wikipedia.org -site:famous-mathematicians.org -site:www.historyandculture.org -site:www.bbc.co.uk -site:www.wikiwand.com -site:philosophiesoflife.org -site:www.ebsco.com -site:www.world-of-mathematics.com -site:humanidades.com -site:plato.sydney.edu.au -site:simple.wikipedia.org -site:www.thoughtco.com