euclidean Geometry where the parallel line postulate exists. and the is also eliptic geometry where the parallel line postulate does not exist.
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geometry
In normal geometry, it's not possible to make a triangle with two obtuse angles. It is possible to make a triangle with two obtuse angles in spherical geometry -- it's a kind of "spherical triangle". It is possible to make a triangle with two obtuse angles in some kinds of non-Euclidean geometry -- it's a kind of "non-Euclidean triangle".
Two dimensional geometry is called "plane geometry" meaning that it occurs on a single surface or plane. The objects used in plane geometry are called plane figures.
Presumably it is simply geometry. However, plane geometry is geometry which is limited to objects with up to two dimensions, that is, objects that lie in a plane - or on a flat surface.
a plane