Conjugate hyperbola

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A hyperbola and its conjugate hyperbola Hyperbler konjugerte.png
A hyperbola and its conjugate hyperbola

In geometry, a conjugate hyperbola to a given hyperbola shares the same asymptotes but lies in the opposite two sectors of the plane compared to the original hyperbola.

Contents

A hyperbola and its conjugate may be constructed as conic sections derived from an intersecting plane and cutting tangent double cones sharing the same apex.

Construction

Two cones with common apex at the origin are tangent along the lines y = mx and y = –mx. The cone around the x-axis is

and the one about the y-axis is

The intersections with plane z = b yield two hyperbolas:

or equivalently

These hyperbolas are conjugate with respect to each other.

The rectangular case is recovered with m = 1 = b.

History

Light cone and conjugate hyperbolas in Minkowski (1908) Minkowski2.png
Light cone and conjugate hyperbolas in Minkowski (1908)

The conjugate hyperbola arises in the study of conjugate diameters of conic sections.

Elements of Dynamic (1878) by W. K. Clifford identifies the conjugate hyperbola. [1]

In 1894 Alexander Macfarlane used an illustration of conjugate right hyperbolas in his study "Principles of elliptic and hyperbolic analysis". [2]

In 1895 W. H. Besant noted conjugate hyperbolas in his book on conic sections. [3] George Salmon illustrated a conjugate hyperbola as a dotted curve in this Treatise on Conic Sections (1900). [4]

In 1908 conjugate hyperbolas were used by Herman Minkowski to demarcate units of duration and distance in a spacetime diagram illustrating a plane in his Minkowski space. [5]

The principle of relativity may be stated as "Any pair of conjugate diameters of conjugate hyperbolas can be taken for the axes of space and time". [6]

In 1957 Barry Spain illustrated conjugate rectangular hyperbolas. [7]

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References

  1. W. K. Clifford (1878) Elements of Dynamic, page 90, via Internet Archive
  2. Alexander Macfarlane (1894) Principles of Space Analysis via Internet Archive
  3. W. H. Besant (1895) Conic Sections Treated Geometrically, page 25 via HathiTrust
  4. George Salmon (1900) A Treatise on Conic Sections via Internet Archive
  5. Minkowski, Hermann (1907–1908), "Die Grundgleichungen für die elektromagnetischen Vorgänge in bewegten Körpern"  [The Fundamental Equations for Electromagnetic Processes in Moving Bodies], Nachrichten von der Gesellschaft der Wissenschaften zu Göttingen, Mathematisch-Physikalische Klasse: 53–111
  6. Whittaker, E.T. (1910). A History of the Theories of Aether and Electricity (1 ed.). Dublin: Longman, Green and Co. p.  441.
  7. Barry Spain (1957) Analytical Conics via HathiTrust