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  2. 3-sphere - Wikipedia

    en.wikipedia.org/wiki/3-sphere

    A 3-sphere can be constructed topologically by "gluing" together the boundaries of a pair of 3-balls. The boundary of a 3-ball is a 2-sphere, and these two 2-spheres are to be identified. That is, imagine a pair of 3-balls of the same size, then superpose them so that their 2-spherical boundaries match, and let matching pairs of points on the ...

  3. Monge's theorem - Wikipedia

    en.wikipedia.org/wiki/Monge's_theorem

    The three spheres can be sandwiched uniquely between two planes. Each pair of spheres defines a cone that is externally tangent to both spheres, and the apex of this cone corresponds to the intersection point of the two external tangents, i.e., the external homothetic center. Since one line of the cone lies in each plane, the apex of each cone ...

  4. Intersection (geometry) - Wikipedia

    en.wikipedia.org/wiki/Intersection_(geometry)

    There are two possibilities: if =, the spheres coincide, and the intersection is the entire sphere; if , the spheres are disjoint and the intersection is empty. When a is nonzero, the intersection lies in a vertical plane with this x-coordinate, which may intersect both of the spheres, be tangent to both spheres, or external to both spheres.

  5. Spherical geometry - Wikipedia

    en.wikipedia.org/wiki/Spherical_geometry

    In the extrinsic 3-dimensional picture, a great circle is the intersection of the sphere with any plane through the center. In the intrinsic approach, a great circle is a geodesic; a shortest path between any two of its points provided they are close enough. Or, in the (also intrinsic) axiomatic approach analogous to Euclid's axioms of plane ...

  6. Line–sphere intersection - Wikipedia

    en.wikipedia.org/wiki/Line–sphere_intersection

    The three possible line-sphere intersections: 1. No intersection. 2. Point intersection. 3. Two point intersection. In analytic geometry, a line and a sphere can intersect in three ways: No intersection at all; Intersection in exactly one point; Intersection in two points.

  7. Homology sphere - Wikipedia

    en.wikipedia.org/wiki/Homology_sphere

    If p, q, and r are pairwise relatively prime positive integers then the link of the singularity x p + y q + z r = 0 (in other words, the intersection of a small 3-sphere around 0 with this complex surface) is a Brieskorn manifold that is a homology 3-sphere, called a Brieskorn 3-sphere Σ(p, q, r).

  8. Sphere - Wikipedia

    en.wikipedia.org/wiki/Sphere

    The angle between two spheres at a real point of intersection is the dihedral angle determined ... had created even more nearly perfect spheres, accurate to 0.3 ...

  9. Constant chord theorem - Wikipedia

    en.wikipedia.org/wiki/Constant_chord_theorem

    A similar theorem exists in three dimensions for the intersection of two spheres. The spheres k 1 {\displaystyle k_{1}} and k 2 {\displaystyle k_{2}} intersect in the circle k s {\displaystyle k_{s}} .