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  2. Arrangement of lines - Wikipedia

    en.wikipedia.org/wiki/Arrangement_of_lines

    Another type of non-Euclidean geometry is the hyperbolic plane, and arrangements of lines in this geometry have also been studied. [50] Any finite set of lines in the Euclidean plane has a combinatorially equivalent arrangement in the hyperbolic plane (e.g. by enclosing the vertices of the arrangement by a large circle and interpreting the ...

  3. Cevian - Wikipedia

    en.wikipedia.org/wiki/Cevian

    In geometry, a cevian is a line segment which joins a vertex of a triangle to a point on the opposite side of the triangle. [ 1 ] [ 2 ] Medians and angle bisectors are special cases of cevians. The name "cevian" comes from the Italian mathematician Giovanni Ceva , who proved a well-known theorem about cevians which also bears his name.

  4. Line (geometry) - Wikipedia

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

    Here, p is the (positive) length of the line segment perpendicular to the line and delimited by the origin and the line, and is the (oriented) angle from the x-axis to this segment. It may be useful to express the equation in terms of the angle α = φ + π / 2 {\displaystyle \alpha =\varphi +\pi /2} between the x -axis and the line.

  5. Perpendicular - Wikipedia

    en.wikipedia.org/wiki/Perpendicular

    The segment AB is perpendicular to the segment CD because the two angles it creates (indicated in orange and blue) are each 90 degrees. The segment AB can be called the perpendicular from A to the segment CD, using "perpendicular" as a noun. The point B is called the foot of the perpendicular from A to segment CD, or simply, the foot of A on CD ...

  6. Angle of incidence (optics) - Wikipedia

    en.wikipedia.org/wiki/Angle_of_incidence_(optics)

    In computer graphics and geography, the angle of incidence is also known as the illumination angle of a surface with a light source, such as the Earth's surface and the Sun. [1] It can also be equivalently described as the angle between the tangent plane of the surface and another plane at right angles to the light rays. [ 2 ]

  7. Carnot's theorem (perpendiculars) - Wikipedia

    en.wikipedia.org/wiki/Carnot's_theorem...

    Carnot's theorem: if three perpendiculars on triangle sides intersect in a common point F, then blue area = red area. Carnot's theorem (named after Lazare Carnot) describes a necessary and sufficient condition for three lines that are perpendicular to the (extended) sides of a triangle having a common point of intersection.

  8. Hilbert's axioms - Wikipedia

    en.wikipedia.org/wiki/Hilbert's_axioms

    Then in the plane α′ there is one and only one ray k′ such that the angle ∠ (h, k), or ∠ (k, h), is congruent to the angle ∠ (h′, k′) and at the same time all interior points of the angle ∠ (h′, k′) lie upon the given side of a′. We express this relation by means of the notation ∠ (h, k) ≅ ∠ (h′, k′).

  9. Incidence geometry - Wikipedia

    en.wikipedia.org/wiki/Incidence_geometry

    In mathematics, incidence geometry is the study of incidence structures. A geometric structure such as the Euclidean plane is a complicated object that involves concepts such as length, angles, continuity, betweenness, and incidence .