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  2. Collinearity - Wikipedia

    en.wikipedia.org/wiki/Collinearity

    For instance, in spherical geometry, where lines are represented in the standard model by great circles of a sphere, sets of collinear points lie on the same great circle. Such points do not lie on a "straight line" in the Euclidean sense, and are not thought of as being in a row.

  3. Circumcircle - Wikipedia

    en.wikipedia.org/wiki/Circumcircle

    The circumcircle of three collinear points is the line on which the three points lie, often referred to as a circle of infinite radius. Nearly collinear points often lead to numerical instability in computation of the circumcircle. Circumcircles of triangles have an intimate relationship with the Delaunay triangulation of a set of points.

  4. Circle - Wikipedia

    en.wikipedia.org/wiki/Circle

    The distance between any point of the circle and the centre is called the radius. The length of a line segment connecting two points on the circle and passing through the centre is called the diameter. A circle bounds a region of the plane called a disc. The circle has been known since before the beginning of recorded history.

  5. Area of a circle - Wikipedia

    en.wikipedia.org/wiki/Area_of_a_circle

    Let one side of an inscribed regular n-gon have length s n and touch the circle at points A and B. Let A′ be the point opposite A on the circle, so that A′A is a diameter, and A′AB is an inscribed triangle on a diameter. By Thales' theorem, this is a right triangle with right angle at B.

  6. Five points determine a conic - Wikipedia

    en.wikipedia.org/wiki/Five_points_determine_a_conic

    These results seem to run counter the general result since circles are special cases of conics. However, in a pappian projective plane a conic is a circle only if it passes through two specific points on the line at infinity, so a circle is determined by five non-collinear points, three in the affine plane and these two special points. Similar ...

  7. Collineation - Wikipedia

    en.wikipedia.org/wiki/Collineation

    Möbius' designation can be expressed by saying, collinear points are mapped by a permutation to collinear points, or in plain speech, straight lines stay straight. Contemporary mathematicians view geometry as an incidence structure with an automorphism group consisting of mappings of the underlying space that preserve incidence. Such a mapping ...

  8. Cross-ratio - Wikipedia

    en.wikipedia.org/wiki/Cross-ratio

    Being on a circle means the four points are the image of four real points under a Möbius transformation, and hence the cross ratio is a real number. The Poincaré half-plane model and Poincaré disk model are two models of hyperbolic geometry in the complex projective line .

  9. Collinearity equation - Wikipedia

    en.wikipedia.org/wiki/Collinearity_equation

    The equations originate from the central projection of a point of the object through the optical centre of the camera to the image on the sensor plane. [1] The three points P, Q and R are projected on the plane S through the projection centre C x- and z-axis of the projection of P through the projection centre C