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  "body": "\n## Summary\n\nSpherical geometry is the geometry of the surface of a sphere, where the role of lines is played by great circles.\nAny two great circles meet, so there are no parallel lines, and the angle sum of a triangle exceeds $\\pi$.\nIt is the oldest [[non-Euclidean geometry|SPCYMFN5V2]] in practice, used for navigation and astronomy long before the axioms of geometry were questioned.\nIdentifying antipodal points turns it into [[elliptic geometry|H5GB19W2H3]].\n\n## Explanations\n\n### L1 human\n\nOn a globe, the shortest route between two cities follows a great circle, a circle whose centre is the centre of the Earth.\nThese great circles are the straight lines of spherical geometry.\nThe equator and any meridian are great circles; the circles of latitude other than the equator are not.\nA triangle with one corner at the North Pole and two on the equator, a quarter turn apart, has three right angles.\n",
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