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  2. Arithmetic - Wikipedia

    en.wikipedia.org/wiki/Arithmetic

    Analytic number theory, by contrast, relies on techniques from analysis and calculus. It examines problems like how prime numbers are distributed and the claim that every even number is a sum of two prime numbers. [83] Algebraic number theory employs algebraic structures to analyze the properties of and relations between numbers.

  3. Modular arithmetic - Wikipedia

    en.wikipedia.org/wiki/Modular_arithmetic

    In chemistry, the last digit of the CAS registry number (a unique identifying number for each chemical compound) is a check digit, which is calculated by taking the last digit of the first two parts of the CAS registry number times 1, the previous digit times 2, the previous digit times 3 etc., adding all these up and computing the sum modulo 10.

  4. Quadratic formula - Wikipedia

    en.wikipedia.org/wiki/Quadratic_formula

    The quadratic formula is exactly correct when performed using the idealized arithmetic of real numbers, but when approximate arithmetic is used instead, for example pen-and-paper arithmetic carried out to a fixed number of decimal places or the floating-point binary arithmetic available on computers, the limitations of the number representation ...

  5. Calculator - Wikipedia

    en.wikipedia.org/wiki/Calculator

    By 1970, a calculator could be made using just a few chips of low power consumption, allowing portable models powered from rechargeable batteries. The first handheld calculator was a 1967 prototype called Cal Tech, whose development was led by Jack Kilby at Texas Instruments in a research project to produce a portable calculator. It could add ...

  6. Mathematics - Wikipedia

    en.wikipedia.org/wiki/Mathematics

    A Cauchy sequence consists of elements such that all subsequent terms of a term become arbitrarily close to each other as the sequence progresses (from left to right). Calculus, formerly called infinitesimal calculus, was introduced independently and simultaneously by 17th-century mathematicians Newton and Leibniz . [ 39 ]

  7. Lemniscate elliptic functions - Wikipedia

    en.wikipedia.org/wiki/Lemniscate_elliptic_functions

    The lemniscate functions have periods related to a number = 2.622057... called the lemniscate constant, the ratio of a lemniscate's perimeter to its diameter. This number is a quartic analog of the ( quadratic ) π = {\displaystyle \pi =} 3.141592... , ratio of perimeter to diameter of a circle .

  8. Manning formula - Wikipedia

    en.wikipedia.org/wiki/Manning_formula

    The discharge formula, Q = A V, can be used to rewrite Gauckler–Manning's equation by substitution for V. Solving for Q then allows an estimate of the volumetric flow rate (discharge) without knowing the limiting or actual flow velocity. The formula can be obtained by use of dimensional analysis.

  9. Birth control - Wikipedia

    en.wikipedia.org/wiki/Birth_control

    Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent pregnancy. [1] [2] Birth control has been used since ancient times, but effective and safe methods of birth control only became available in the 20th century. [3]