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  2. Exponential sum - Wikipedia

    en.wikipedia.org/wiki/Exponential_sum

    If the sum is of the form = ()where ƒ is a smooth function, we could use the Euler–Maclaurin formula to convert the series into an integral, plus some corrections involving derivatives of S(x), then for large values of a you could use "stationary phase" method to calculate the integral and give an approximate evaluation of the sum.

  3. Euler's formula - Wikipedia

    en.wikipedia.org/wiki/Euler's_formula

    Substituting r(cos θ + i sin θ) for e ix and equating real and imaginary parts in this formula gives ⁠ dr / dx ⁠ = 0 and ⁠ dθ / dx ⁠ = 1. Thus, r is a constant, and θ is x + C for some constant C. The initial values r(0) = 1 and θ(0) = 0 come from e 0i = 1, giving r = 1 and θ = x.

  4. Euler's identity - Wikipedia

    en.wikipedia.org/wiki/Euler's_identity

    It can be seen that as N gets larger (1 + ⁠ iπ / N ⁠) N approaches a limit of −1. Euler's identity asserts that e i π {\displaystyle e^{i\pi }} is equal to −1. The expression e i π {\displaystyle e^{i\pi }} is a special case of the expression e z {\displaystyle e^{z}} , where z is any complex number .

  5. Pfister's sixteen-square identity - Wikipedia

    en.wikipedia.org/wiki/Pfister's_sixteen-square...

    with the bilinear functions of the and is possible only for n ∈ {1, 2, 4, 8} . However, the more general Pfister's theorem (1965) shows that if the z i {\displaystyle z_{i}} are rational functions of one set of variables, hence has a denominator , then it is possible for all n = 2 m {\displaystyle n=2^{m}} . [ 3 ]

  6. Summation by parts - Wikipedia

    en.wikipedia.org/wiki/Summation_by_parts

    It may be used to prove Nicomachus's theorem that the sum of the first cubes equals the square of the sum of the first positive integers. [2] Summation by parts is frequently used to prove Abel's theorem and Dirichlet's test.

  7. Quater-imaginary base - Wikipedia

    en.wikipedia.org/wiki/Quater-imaginary_base

    Most numbers have a unique quater-imaginary representation, but just as 1 has the two representations 1 = 0. 9 in decimal notation, so, because of 0. 0001 2i = ⁠ 1 / 15 ⁠, the number ⁠ 1 / 5 ⁠ has the two quater-imaginary representations 0. 0003 2i = 3· ⁠ 1 / 15 ⁠ = ⁠ 1 / 5 ⁠ = 1 + 3· ⁠ –4 / 15 ⁠ = 1. 0300 2i.

  8. AOL Mail

    mail.aol.com

    You can find instant answers on our AOL Mail help page. Should you need additional assistance we have experts available around the clock at 800-730-2563.

  9. Fermat's theorem on sums of two squares - Wikipedia

    en.wikipedia.org/wiki/Fermat's_theorem_on_sums_of...

    Fermat's theorem on sums of two squares is strongly related with the theory of Gaussian primes.. A Gaussian integer is a complex number + such that a and b are integers. The norm (+) = + of a Gaussian integer is an integer equal to the square of the absolute value of the Gaussian integer.