'It's any system of geometry not based on the system in "Elements", a book from around 300 B.C.'
non-Euclidean
MATH: Its any system of geometry not based on the system in Elements, a book from around 300 B.C.
It's any system of geometry not based on the system in "Elements", a book from around 300 B.C.
It's any system of geometry not based on the system in "Elements", a book from around 300 B.C.
MATH
non-Euclidean
MATH