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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. Jacobi elliptic functions - Wikipedia

    en.wikipedia.org/wiki/Jacobi_elliptic_functions

    Plot of the Jacobi ellipse (x 2 + y 2 /b 2 = 1, b real) and the twelve Jacobi elliptic functions pq(u,m) for particular values of angle φ and parameter b. The solid curve is the ellipse, with m = 1 − 1/b 2 and u = F(φ,m) where F(⋅,⋅) is the elliptic integral of the first kind (with parameter =). The dotted curve is the unit circle.

  4. 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.

  5. Elliptic function - Wikipedia

    en.wikipedia.org/wiki/Elliptic_function

    Except for a comment by Landen [14] his ideas were not pursued until 1786, when Legendre published his paper Mémoires sur les intégrations par arcs d’ellipse. [15] Legendre subsequently studied elliptic integrals and called them elliptic functions. Legendre introduced a three-fold classification –three kinds– which was a crucial ...

  6. Ellipse - Wikipedia

    en.wikipedia.org/wiki/Ellipse

    Then the free end of the strip traces an ellipse, while the strip is moved. For the proof, one recognizes that the tracing point can be described parametrically by ( a cos ⁡ t , b sin ⁡ t ) {\displaystyle (a\cos t,\,b\sin t)} , where parameter t {\displaystyle t} is the angle of slope of the paper strip.

  7. 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} .

  8. Elliptic geometry - Wikipedia

    en.wikipedia.org/wiki/Elliptic_geometry

    The distance formula is homogeneous in each variable, with d(λu, μv) = d(u, v) if λ and μ are non-zero scalars, so it does define a distance on the points of projective space. A notable property of the projective elliptic geometry is that for even dimensions, such as the plane, the geometry is non-orientable. It erases the distinction ...

  9. Non-Euclidean geometry - Wikipedia

    en.wikipedia.org/wiki/Non-Euclidean_geometry

    In mathematics, non-Euclidean geometry consists of two geometries based on axioms closely related to those that specify Euclidean geometry.As Euclidean geometry lies at the intersection of metric geometry and affine geometry, non-Euclidean geometry arises by either replacing the parallel postulate with an alternative, or relaxing the metric requirement.