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  2. Projective plane - Wikipedia

    en.wikipedia.org/wiki/Projective_plane

    a + b = T(a, 1, b), and a ⋅ b = T(a, b, 0). The ternary operator is linear if T(x, m, k) = x⋅m + k. When the set of coordinates of a projective plane actually form a ring, a linear ternary operator may be defined in this way, using the ring operations on the right, to produce a planar ternary ring.

  3. Duality (projective geometry) - Wikipedia

    en.wikipedia.org/wiki/Duality_(projective_geometry)

    This correlation would also map a line determined by two points (a 1, b 1, c 1, d 1) and (a 2, b 2, c 2, d 2) to the line which is the intersection of the two planes with equations a 1 x + b 1 y + c 1 z + d 1 w = 0 and a 2 x + b 2 y + c 2 z + d 2 w = 0. The associated sesquilinear form for this correlation is: φ(u, x) = u H ⋅ x P = u 0 x 0 ...

  4. Parabola - Wikipedia

    en.wikipedia.org/wiki/Parabola

    Remark 1: The 2-points–2-tangents property of a parabola is an affine version of the 3-point degeneration of Pascal's theorem. Remark 2: The 2-points–2-tangents property should not be confused with the following property of a parabola, which also deals with 2 points and 2 tangents, but is not related to Pascal's theorem.

  5. Line at infinity - Wikipedia

    en.wikipedia.org/wiki/Line_at_infinity

    Also, if any pair of lines do not intersect at a point on the line, then the pair of lines are parallel. Every line intersects the line at infinity at some point. The point at which the parallel lines intersect depends only on the slope of the lines, not at all on their y-intercept. In the affine plane, a line extends in two opposite directions.

  6. Parallel (geometry) - Wikipedia

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

    the distance between the two lines can be found by locating two points (one on each line) that lie on a common perpendicular to the parallel lines and calculating the distance between them. Since the lines have slope m, a common perpendicular would have slope1/m and we can take the line with equation y = −x/m as a common perpendicular ...

  7. Asymptote - Wikipedia

    en.wikipedia.org/wiki/Asymptote

    For a conic, there are a pair of lines that do not intersect the conic at any complex point: these are the two asymptotes of the conic. A plane algebraic curve is defined by an equation of the form P(x,y) = 0 where P is a polynomial of degree n

  8. Euclidean planes in three-dimensional space - Wikipedia

    en.wikipedia.org/wiki/Euclidean_planes_in_three...

    When the intersection of a sphere and a plane is not empty or a single point, it is a circle. This can be seen as follows: Let S be a sphere with center O, P a plane which intersects S. Draw OE perpendicular to P and meeting P at E. Let A and B be any two different points in the intersection.

  9. Scheinerman's conjecture - Wikipedia

    en.wikipedia.org/wiki/Scheinerman's_conjecture

    In mathematics, Scheinerman's conjecture, now a theorem, states that every planar graph is the intersection graph of a set of line segments in the plane. This conjecture was formulated by E. R. Scheinerman in his Ph.D. thesis , following earlier results that every planar graph could be represented as the intersection graph of a set of simple curves in the plane (Ehrlich, Even & Tarjan 1976).