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  2. Rhombic antenna - Wikipedia

    en.wikipedia.org/wiki/Rhombic_antenna

    The length is not critical, typically from one to two wavelengths end-to-end, but for any given length and frequency, there is an optimum acute angle at which the sections should meet. A horizontal rhombic antenna radiates horizontally polarized radio waves at a low elevation angle off the acute end of the antenna opposite the feedline.

  3. Spherical coordinate system - Wikipedia

    en.wikipedia.org/wiki/Spherical_coordinate_system

    Even with these restrictions, if the polar angle (inclination) is 0° or 180°—elevation is −90° or +90°—then the azimuth angle is arbitrary; and if r is zero, both azimuth and polar angles are arbitrary. To define the coordinates as unique, the user can assert the convention that (in these cases) the arbitrary coordinates are set to zero.

  4. Rhombohedron - Wikipedia

    en.wikipedia.org/wiki/Rhombohedron

    For a unit (i.e.: with side length 1) rhombohedron, [4] with rhombic acute angle , with one vertex at the origin (0, 0, 0), and with one edge lying along the x-axis, the three generating vectors are

  5. Grade (slope) - Wikipedia

    en.wikipedia.org/wiki/Grade_(slope)

    α = angle of inclination. The grade (US) or gradient (UK) (also called stepth, slope, incline, mainfall, pitch or rise) of a physical feature, landform or constructed line is either the elevation angle of that surface to the horizontal or its tangent. It is a special case of the slope, where zero indicates horizontality. A larger number ...

  6. Angle of arrival - Wikipedia

    en.wikipedia.org/wiki/Angle_of_arrival

    The aim is either for the cell system to report the location of a cell phone placing an emergency call or to provide a service to tell the user of the cell phone where they are. Multiple receivers on a base station would calculate the AoA of the cell phone's signal, and this information would be combined to determine the phone's location.

  7. Axis–angle representation - Wikipedia

    en.wikipedia.org/wiki/Axis–angle_representation

    The angle θ and axis unit vector e define a rotation, concisely represented by the rotation vector θe.. In mathematics, the axis–angle representation parameterizes a rotation in a three-dimensional Euclidean space by two quantities: a unit vector e indicating the direction of an axis of rotation, and an angle of rotation θ describing the magnitude and sense (e.g., clockwise) of the ...

  8. Solid angle - Wikipedia

    en.wikipedia.org/wiki/Solid_angle

    The solid angle of a sphere measured from any point in its interior is 4 π sr. The solid angle subtended at the center of a cube by one of its faces is one-sixth of that, or 2 π /3 sr. The solid angle subtended at the corner of a cube (an octant) or spanned by a spherical octant is π /2 sr, one-eight of the solid angle of a sphere. [1]

  9. Fresnel rhomb - Wikipedia

    en.wikipedia.org/wiki/Fresnel_rhomb

    On the angle-of-incidence scale (horizontal axis), Brewster's angle is where δ p (red) falls from 180° to 0°, and the critical angle is where both δ p and δ s (red and blue) start to rise again. To the left of the critical angle is the region of partial reflection; here both reflection coefficients are real (phase 0° or 180°) with ...