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  2. 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, and 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. Solid angles can also be measured in square degrees (1 sr = (180/ π) 2 square degrees), in square arc-minutes and square arc-seconds, or in fractions of ...

  3. Steradian - Wikipedia

    en.wikipedia.org/wiki/Steradian

    1 m 2 /m 2. square degrees. 1802 / π2⁠ deg2. ≈ 3 282.8 deg 2. The steradian (symbol: sr) or square radian[1][2] is the unit of solid angle in the International System of Units (SI). It is used in three dimensional geometry, and is analogous to the radian, which quantifies planar angles. A solid angle in steradians, projected onto a sphere ...

  4. Omega constant - Wikipedia

    en.wikipedia.org/wiki/Omega_constant

    The omega constant is a mathematical constant defined as the unique real number that satisfies the equation. It is the value of W(1), where W is Lambert's W function. The name is derived from the alternate name for Lambert's W function, the omega function. The numerical value of Ω is given by.

  5. List of trigonometric identities - Wikipedia

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

    Ptolemy's theorem states that the sum of the products of the lengths of opposite sides is equal to the product of the lengths of the diagonals. When those side-lengths are expressed in terms of the sin and cos values shown in the figure above, this yields the angle sum trigonometric identity for sine: sin( α + β ) = sin α cos β + cos α sin ...

  6. Lambda cube - Wikipedia

    en.wikipedia.org/wiki/Lambda_cube

    The lambda cube. Direction of each arrow is direction of inclusion. In mathematical logic and type theory, the λ-cube (also written lambda cube) is a framework introduced by Henk Barendregt [1] to investigate the different dimensions in which the calculus of constructions is a generalization of the simply typed λ-calculus.

  7. Debye model - Wikipedia

    en.wikipedia.org/wiki/Debye_model

    The Debye model is a solid-state equivalent of Planck's law of black body radiation, which treats electromagnetic radiation as a photon gas confined in a vacuum space. Correspondingly, the Debye model treats atomic vibrations as phonons confined in the solid's volume. Most of the calculation steps are identical, as both are examples of a ...

  8. Friedmann equations - Wikipedia

    en.wikipedia.org/wiki/Friedmann_equations

    To date, the critical density is estimated to be approximately five atoms (of monatomic hydrogen) per cubic metre, whereas the average density of ordinary matter in the Universe is believed to be 0.2–0.25 atoms per cubic metre. [4] [5] Estimated relative distribution for components of the energy density of the universe.

  9. Complex number - Wikipedia

    en.wikipedia.org/wiki/Complex_number

    Complex number. A complex number can be visually represented as a pair of numbers (a, b) forming a vector on a diagram called an Argand diagram, representing the complex plane. Re is the real axis, Im is the imaginary axis, and i is the "imaginary unit", that satisfies i2 = −1. In mathematics, a complex number is an element of a number system ...