R2 (and 4/3 R3).
Figure: this website
Different Spatial Geometries |
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Geometry in non-Euclidean space differs from our intuitive geometry of "flat" (ie
Euclidean) space. Paralell lines can meet and/or diverge; triangles can have interior angles which need not sum to 180 degrees; and the areas (and volumes) of
circles (and spheres) do not follow the "flat space" formulae R2 (and 4/3 R3).
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Figure: this website | |