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  2. Tangent lines to circles - Wikipedia

    en.wikipedia.org/wiki/Tangent_lines_to_circles

    Two radial lines may be drawn from the center O 1 through the tangent points on C 3; these intersect C 1 at the desired tangent points. The desired external tangent lines are the lines perpendicular to these radial lines at those tangent points, which may be constructed as described above. Internal tangents Construction of the inner tangent

  3. Pushforward (differential) - Wikipedia

    en.wikipedia.org/wiki/Pushforward_(differential)

    If a map, φ, carries every point on manifold M to manifold N then the pushforward of φ carries vectors in the tangent space at every point in M to a tangent space at every point in N. In differential geometry , pushforward is a linear approximation of smooth maps (formulating manifold) on tangent spaces.

  4. Inversive geometry - Wikipedia

    en.wikipedia.org/wiki/Inversive_geometry

    A circle that passes through the center O of the reference circle inverts to a line not passing through O, but parallel to the tangent to the original circle at O, and vice versa; whereas a line passing through O is inverted into itself (but not pointwise invariant). [5] A circle not passing through O inverts to a circle not passing through O ...

  5. Soddy circles of a triangle - Wikipedia

    en.wikipedia.org/wiki/Soddy_circles_of_a_triangle

    When the outer Soddy circle has negative curvature, its center is the isoperimetric point of the triangle: the three triangles formed by this center and two vertices of the starting triangle all have the same perimeter. [4] Triangles whose outer Soddy circle degenerates to a straight line with curvature zero have been called "Soddyian triangles ...

  6. Tangent - Wikipedia

    en.wikipedia.org/wiki/Tangent

    The tangent plane to a surface at a given point p is defined in an analogous way to the tangent line in the case of curves. It is the best approximation of the surface by a plane at p , and can be obtained as the limiting position of the planes passing through 3 distinct points on the surface close to p as these points converge to p .

  7. Central cylindrical projection - Wikipedia

    en.wikipedia.org/wiki/Central_cylindrical_projection

    The central cylindrical projection is a perspective cylindrical map projection. It corresponds to projecting the Earth's surface onto a cylinder tangent to the equator as if from a light source at Earth's center. The cylinder is then cut along one of the projected meridians and unrolled into a flat map. [1]

  8. Map projection - Wikipedia

    en.wikipedia.org/wiki/Map_projection

    Distance from the tangent point on the map is proportional to straight-line distance through the Earth: r(d) = c sin ⁠ d / 2R ⁠ [38] Logarithmic azimuthal is constructed so that each point's distance from the center of the map is the logarithm of its distance from the tangent point on the Earth.

  9. Ford circle - Wikipedia

    en.wikipedia.org/wiki/Ford_circle

    Each circle is tangent to the base line and its neighboring circles. Irreducible fractions with the same denominator have circles of the same size. In mathematics, a Ford circle is a circle in the Euclidean plane, in a family of circles that are all tangent to the -axis at rational points.