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  2. Conjugate diameters - Wikipedia

    en.wikipedia.org/wiki/Conjugate_diameters

    For an ellipse, two diameters are conjugate if and only if the tangent line to the ellipse at an endpoint of one diameter is parallel to the other diameter. Each pair of conjugate diameters of an ellipse has a corresponding tangent parallelogram, sometimes called a bounding parallelogram (skewed compared to a bounding rectangle).

  3. List of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/List_of_trigonometric...

    A formula for computing the trigonometric identities for the one-third angle exists, but it requires finding the zeroes of the cubic equation 4x 3 − 3x + d = 0, where is the value of the cosine function at the one-third angle and d is the known value of the cosine function at the full angle.

  4. Parallel curve - Wikipedia

    en.wikipedia.org/wiki/Parallel_curve

    Thus, the general offset surface shares the same tangent plane and normal with and (()). That aligns with the nature of envelopes. That aligns with the nature of envelopes. We now consider the Weingarten equations for the shape operator , which can be written as ∂ n → = − ∂ x → S {\displaystyle \partial {\vec {n}}=-\partial {\vec {x}}S} .

  5. Parallelogram - Wikipedia

    en.wikipedia.org/wiki/Parallelogram

    For an ellipse, two diameters are said to be conjugate if and only if the tangent line to the ellipse at an endpoint of one diameter is parallel to the other diameter. Each pair of conjugate diameters of an ellipse has a corresponding tangent parallelogram , sometimes called a bounding parallelogram, formed by the tangent lines to the ellipse ...

  6. Intersecting chords theorem - Wikipedia

    en.wikipedia.org/wiki/Intersecting_chords_theorem

    Next to the tangent-secant theorem and the intersecting secants theorem the intersecting chords theorem represents one of the three basic cases of a more general theorem about two intersecting lines and a circle - the power of point theorem.

  7. Dandelin spheres - Wikipedia

    en.wikipedia.org/wiki/Dandelin_spheres

    The points of tangency F 1, F 2 are the foci of the blue ellipse. The spheres are also tangent to the cone at circles k 1, k 2. For a point P on the ellipse, the tangent segments PF 1 and PF 2 can each be reflected to other tangents of equal length, PF 1 = PP 1 and PF 2 = PP 2, with PP 1 and PP 2 colinear along the ray SP.

  8. Tangential quadrilateral - Wikipedia

    en.wikipedia.org/wiki/Tangential_quadrilateral

    A tangential quadrilateral with its incircle. In Euclidean geometry, a tangential quadrilateral (sometimes just tangent quadrilateral) or circumscribed quadrilateral is a convex quadrilateral whose sides all can be tangent to a single circle within the quadrilateral.

  9. Matrix representation of conic sections - Wikipedia

    en.wikipedia.org/wiki/Matrix_representation_of...

    In mathematics, the matrix representation of conic sections permits the tools of linear algebra to be used in the study of conic sections.It provides easy ways to calculate a conic section's axis, vertices, tangents and the pole and polar relationship between points and lines of the plane determined by the conic.