Like the below......the line.....in the middle is the shared base of one triangle..................it has length of one in my diagram................the distance from point (-1/2, 0) to (1/2, 0)........and u make two lines up............to the top where the two circles connect........since the base has length of one.....both lines are one........the same below..........................

Euclid's elements: proposition 1 - YouTube

▶ 2:03

https://www.youtube.com/watch?v=zdofiH5HncU

 

Jan 28, 2012 - Uploaded by mathematicsonline

Playlist of Euclid's Elements in link below: ... With any straight line you can always create a perfect ...

Euclid's Construction of an Equilateral Triangle - YouTube

▶ 5:05

https://www.youtube.com/watch?v=qHBWL2nCi5Y

Nov 11, 2012 - Uploaded by lilbuschy

This is me explaining Euclid's construction of an equilateral triangle from a given straight line.