2 fixed Euclid refs

In fact, if you look at Euclid's proposition 34 in book 23, and proposition 33 in book 36, this is immediately implied. @Mark Sapir: I am quite sure that people regarded the statement obvious from the beginning of time, but we all know (and the Greeks did too) that obvious is not the same as trivial.

A good version of Euclid's Elements can be found here:

http://farside.ph.utexas.edu/euclid/Elements.pdf

1

In fact, if you look at Euclid's proposition 34 in book 2, and proposition 33 in book 3, this is immediately implied. @Mark Sapir: I am quite sure that people regarded the statement obvious from the beginning of time, but we all know (and the Greeks did too) that obvious is not the same as trivial.

A good version of Euclid's Elements can be found here:

http://farside.ph.utexas.edu/euclid/Elements.pdf