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  2. Angular distance - Wikipedia

    en.wikipedia.org/wiki/Angular_distance

    Angular distance appears in mathematics (in particular geometry and trigonometry) and all natural sciences (e.g., kinematics, astronomy, and geophysics). In the classical mechanics of rotating objects, it appears alongside angular velocity, angular acceleration, angular momentum, moment of inertia and torque.

  3. Angular diameter distance - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter_distance

    The angular size redshift relation for a Lambda cosmology, with on the vertical scale megaparsecs. The angular size redshift relation describes the relation between the angular size observed on the sky of an object of given physical size, and the object's redshift from Earth (which is related to its distance, , from Earth

  4. Cosine similarity - Wikipedia

    en.wikipedia.org/wiki/Cosine_similarity

    The normalized angle, referred to as angular distance, between any two vectors and is a formal distance metric and can be calculated from the cosine similarity. [5] The complement of the angular distance metric can then be used to define angular similarity function bounded between 0 and 1, inclusive.

  5. Standard ruler - Wikipedia

    en.wikipedia.org/wiki/Standard_ruler

    Measuring distances is of great importance in cosmology, as the relationship between the distance and redshift of an object can be used to measure the expansion rate and geometry of the Universe. Distances can also be measured using standard candles ; many different types of standard candles and rulers are needed to construct the cosmic ...

  6. Polar coordinate system - Wikipedia

    en.wikipedia.org/wiki/Polar_coordinate_system

    In green, the point with radial coordinate 3 and angular coordinate 60 degrees or (3, 60°). In blue, the point (4, 210°). In mathematics, the polar coordinate system specifies a given point in a plane by using a distance and an angle as its two coordinates. These are the point's distance from a reference point called the pole, and

  7. Small-angle approximation - Wikipedia

    en.wikipedia.org/wiki/Small-angle_approximation

    In astronomy, the angular size or angle subtended by the image of a distant object is often only a few arcseconds (denoted by the symbol ″), so it is well suited to the small angle approximation. [6] The linear size (D) is related to the angular size (X) and the distance from the observer (d) by the simple formula:

  8. Angular diameter - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter

    The angular diameter, angular size, apparent diameter, or apparent size is an angular separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences , it is called the visual angle , and in optics , it is the angular aperture (of a lens ).

  9. Longitude - Wikipedia

    en.wikipedia.org/wiki/Longitude

    The length of a degree of longitude (east–west distance) depends only on the radius of a circle of latitude. For a sphere of radius a that radius at latitude φ is a cos φ , and the length of a one-degree (or ⁠ π / 180 ⁠ radian ) arc along a circle of latitude is