Just noticed that different materials/sources say different things about the propositions and their proofs in Euclid's Elements. I'm going through and comparing all the videos and materials I can find on proposition I.4.

https://archive.org/details/euclid_heath_2nd_ed/1_euclid_heath_2nd_ed/page/n260/mode/1up?view=theater

http://aleph0.clarku.edu/~djoyce/java/elements/bookI/propI4.html

https://farside.ph.utexas.edu/Books/Euclid/Elements.pdf

https://elements.ratherthanpaper.com/1.4

https://youtu.be/GP6K-2nvZ-Q

https://youtu.be/ejfAWgxydUo

I have done propositions I.1-I.6. I was impressed with 1.1-1.3 and thought they were fun, I was unimpressed with 1.4-I.6 and they were so boring. Hopefully I'll find something interesting and fun about them when I compare all the different sources. Anyway the first three propositions are apparently of a sort called "problems" while the subsequent three propositions are of the other of the two types of propositions in the book, namely "theorems". Problems are so much more fun than theorems. The problems are propositions 1-3, 9-12, 22, 23, 31, 42 and 44-46. The theorems are the rest of the propositions.

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