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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

    More formulas of this nature can be given, as explained by Ramanujan's theory of elliptic functions to alternative bases. Perhaps the most notable hypergeometric inversions are the following two examples, involving the Ramanujan tau function τ {\displaystyle \tau } and the Fourier coefficients j {\displaystyle \mathrm {j} } of the J-invariant ...

  4. Electronic properties of graphene - Wikipedia

    en.wikipedia.org/wiki/Electronic_properties_of...

    Two of the six Dirac points are independent, while the rest are equivalent by symmetry. In the vicinity of the K-points the energy depends linearly on the wave vector, similar to a relativistic particle. [4] [6] Since an elementary cell of the lattice has a basis of two atoms, the wave function has an effective 2-spinor structure.

  5. Euler's identity - Wikipedia

    en.wikipedia.org/wiki/Euler's_identity

    is pi, the ratio of the circumference of a circle to its diameter. Euler's identity is named after the Swiss mathematician Leonhard Euler . It is a special case of Euler's formula e i x = cos ⁡ x + i sin ⁡ x {\displaystyle e^{ix}=\cos x+i\sin x} when evaluated for x = π {\displaystyle x=\pi } .

  6. Leibniz formula for π - Wikipedia

    en.wikipedia.org/wiki/Leibniz_formula_for_π

    The formula is a special case of the Euler–Boole summation formula for alternating series, providing yet another example of a convergence acceleration technique that can be applied to the Leibniz series. In 1992, Jonathan Borwein and Mark Limber used the first thousand Euler numbers to calculate π to 5,263 decimal places with the Leibniz ...

  7. Windows Calculator - Wikipedia

    en.wikipedia.org/wiki/Windows_Calculator

    A simple arithmetic calculator was first included with Windows 1.0. [5]In Windows 3.0, a scientific mode was added, which included exponents and roots, logarithms, factorial-based functions, trigonometry (supports radian, degree and gradians angles), base conversions (2, 8, 10, 16), logic operations, statistical functions such as single variable statistics and linear regression.

  8. Machin-like formula - Wikipedia

    en.wikipedia.org/wiki/Machin-like_formula

    Machin-like formulas for π can be constructed by finding a set of integers , =, where all the prime factorisations of ⁠ + ⁠, taken together, use a number of distinct primes , and then using either linear algebra or the LLL basis-reduction algorithm to construct linear combinations of arctangents of . For example, in the Størmer formula ...

  9. List of equations in quantum mechanics - Wikipedia

    en.wikipedia.org/wiki/List_of_equations_in...

    One particle: N particles: One dimension ^ = ^ + = + ^ = = ^ + (,,) = = + (,,) where the position of particle n is x n. = + = = +. (,) = /.There is a further restriction — the solution must not grow at infinity, so that it has either a finite L 2-norm (if it is a bound state) or a slowly diverging norm (if it is part of a continuum): [1] ‖ ‖ = | |.