János Bolyai and Nikolai Lobachevsky developed a system that was notable  for not following all of this person's rules.
The lemma named for this person states that if a prime number divides a product, then it divides a   factor of that product. János Bolyai and Nikolai Lobachevsky developed a system that was notable  for not following all of this person's rules. A so-called orchard is named for this person because of   his algorithm for finding greatest common divisors. A book he wrote states that if a line segment  intersects two lines, then the lines meet on the side of the segment where the interior angle sum is  less than two right angles, the last of his five postulates. Name this mathematician whose Elements  was a standard text of geometry.
The lemma named for this person states that if a prime number divides a product, then it divides a   factor of that product.
{Euclid} of Alexandria