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  2. Sigma-pi and equivalent-orbital models - Wikipedia

    en.wikipedia.org/wiki/Sigma-pi_and_equivalent...

    The σ-π model differentiates bonds and lone pairs of σ symmetry from those of π symmetry, while the equivalent-orbital model hybridizes them. The σ-π treatment takes into account molecular symmetry and is better suited to interpretation of aromatic molecules ( Hückel's rule ), although computational calculations of certain molecules tend ...

  3. List of formulae involving π - Wikipedia

    en.wikipedia.org/wiki/List_of_formulae_involving_π

    where C is the circumference of a circle, d is the diameter, and r is the radius.More generally, = where L and w are, respectively, the perimeter and the width of any curve of constant width.

  4. Ligand field theory - Wikipedia

    en.wikipedia.org/wiki/Ligand_field_theory

    The other form of coordination π bonding is ligand-to-metal bonding. This situation arises when the π-symmetry p or π orbitals on the ligands are filled. They combine with the d xy, d xz and d yz orbitals on the metal and donate electrons to the resulting π-symmetry bonding orbital between them and the metal. The metal-ligand bond is ...

  5. Trapezoidal rule - Wikipedia

    en.wikipedia.org/wiki/Trapezoidal_rule

    The function f(x) (in blue) is approximated by a linear function (in red). In calculus , the trapezoidal rule (also known as the trapezoid rule or trapezium rule ) [ a ] is a technique for numerical integration , i.e., approximating the definite integral : ∫ a b f ( x ) d x . {\displaystyle \int _{a}^{b}f(x)\,dx.}

  6. Greek letters used in mathematics, science, and engineering

    en.wikipedia.org/wiki/Greek_letters_used_in...

    the Pi function, i.e. the Gamma function when offset to coincide with the factorial; the complete elliptic integral of the third kind; the fundamental groupoid; osmotic pressure; represents: Archimedes' constant (more commonly just called Pi), the ratio of a circle's circumference to its diameter; the prime-counting function

  7. Euler's identity - Wikipedia

    en.wikipedia.org/wiki/Euler's_identity

    The same formula applies to octonions, with a zero real part and a norm equal to 1. These formulas are a direct generalization of Euler's identity, since and are the only complex numbers with a zero real part and a norm (absolute value) equal to 1.

  8. Machin-like formula - Wikipedia

    en.wikipedia.org/wiki/Machin-like_formula

    In mathematics, Machin-like formulas are a popular technique for computing π (the ratio of the circumference to the diameter of a circle) to a large number of digits. They are generalizations of John Machin 's formula from 1706:

  9. List of mathematical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_constants

    For example, the constant π may be defined as the ratio of the length of a circle's circumference to its diameter. The following list includes a decimal expansion and set containing each number, ordered by year of discovery. The column headings may be clicked to sort the table alphabetically, by decimal value, or by set.