¡ßNon-Euclidean Geometry
Parallel postulate, Euclidean the 5th postulate, (¡¸Through a
given point not on a given line can be drawn 'just one' line parallel to the given line.¡¹). This situation is equivalent, respectively, to the fact that the sum of three
internal angles of a triangle is 180 degrees.
This parallel postu late is so complex that it seems like theorem.
Many mathematicians, therefore, made on effort to prove the postulate but satisfactory
results were not made.
So mathematlcians used another way, indirect proof, to deny the
postulate and find out contradictions.
But they only failed to prove the postulate further more they
got new theorems through the way
Finally, they found these new theorems called non-Euclidean geomerry.
¡Ý Saccheri, Girolamo (1667~1733) : These three possibilities are
refered to by Saccheri as the 'hypothesis of the acute angle,'
the 'hypothesis of the right angle', and the 'hypothesis of the
obtuse angle'. He tried to prove these three possibilities
were contradictions
,but rather had admitted his inability to find one, Saccheri
would today unquestionably be credited with the discovery
of non-Euclidean geometry.
¡Ý Lobachevsky : Lobachevsky and Bolyai asserts that parallel postulate is
axiom not tneorem.
He said "Through a given point not on a given line can be drawn
'more than one' line parallel to the given line".
He discovered new geometry.
¡Ý Riemann : He asserted that "Through a given point not on a given line can
be drawn 'no' line parallel to the given line." He discovered consistent geometry.
Ridigity and generalization of abstraction are the characteristics
of Riemann's mathematics.
He widened the geometry to the variety of space.
¡Ý Klein
He classified Euclidean geometry and non-Euclidean geometry
in 1871.
Non-Euclidean geometry means the possibility of another geometry's existence
except Euclidean geometry.
It, therefore, is clear that mathematicians don't have to cling
to practical physical space.