This is slightly contradictory, as the Pythagorean theorem doesn't really have any meaning unless Euclid's postulates have already been established. It seems that they couldn't have been, as Euclid was still about -200 years old during Pythagoras' time (which was, in case you're wondering, around 500 BC), but actually, Euclid didn't really make up much stuff; he just put other people's ideas and assumptions all together in a treatise titled Elements, though I am as of yet unsure where he got the title from.
Figure 1
