It was "A. Pythagoras" who was the Greek mathematician who systematized geometry and wrote a textbook that organized all the existing information about geometry, although many other Greeks were well-versed in this subject.
I had a quiz recently with this question on it and I entered A. Pythagoras but it told me I was wrong and said the correct answer was B. Euclid If there is a misunderstanding about the question please let me know and id be happy to fix my mistake. I have proof too for my mistake. Lol. Have a great day!