# Euler's Formula

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## Euler's formula

[′ȯi·lərz ‚fȯr·myə·lə]
(mathematics)
The formula e ix = cos x + i sin x, where i = √(-1).

## Euler’s Formula

any of several important formulas established by L. Euler.

(1) A formula giving the relation between the exponential function and trigonometric functions (1743):

eix = cos x + i sin x

Also known as Euler’s formulas are the equations

(2) A formula giving the expansion of the function sin x in an infinite product (1740):

(3) The formula

where s = 1,2,... and p runs over all prime numbers.

(4) The formula

(a2 + b2 + c2 + d2)(p2 + q2 + r2 + s2) = x2 + y2 + z2 + t2

where

x = ap + bq + cr + ds

y = aqbp ± csdr

z = arbscp ± dq

t = as ± brcqdp

(5) The formula (1760)

Also known as the equation of Euler, it gives an expression for the curvature 1/R of a normal section of a surface in terms of the surface’s principal curvatures 1/R1 and 1/R2 and the angle φ between one of the principal directions and the given direction.

Other well-known formulas associated with Euler include the Euler-Maclaurin summation formula and the Euler-Fourier formulas for the coefficients of expansions of functions in trigonometric series.

References in periodicals archive ?
Many of these entities have been given simple and ambiguous names such as Euler's function, Euler's equation, and Euler's formula.
If every face of the cube was the base for an attached square pyramid, this three-dimensional star-like object would have V = 14, F = 24, E = 36, which again satisfies Euler's formula.
Yes, there are formulas throughout these pages, strings of numbers--real and imaginary--and explanations of primes and logarithms, Fermat's Last Theorem and Euler's formula, but no matter how much you hated math in high school, you can't help but be seduced by the housekeeper's enthusiasm for what she discovers.
2) and summing up Leibniz's series, we obtain another Euler's formula
As an example, it can be applied to prove Euler's formula automatically.
Now in an updated and expanded third edition, "A Concise Introduction To Pure Mathematics" by Martin Liebeck provides an informed and informative presentation into a representative selection of fundamental ideas in mathematics including the theory of solving cubic equations, the use of Euler's formula to study the five Platonic solids, the use of prime numbers to encode and decode secret information, the theory of how to compare the sizes of two infinite sets, the limits of sequences and continuous functions, the use of the intermediate value theorem to prove the existence of nth roots, and so much more.
For any regular or semi-regular polyhedron, Euler's formula holds, and the vertices are all alike.
Among the topics are modular functions and Eisenstein series, the Riemann zeta function, Euler's formulas and functional equations, functional equations, a linear space of solutions, and the multidimensional Poisson summation formula.

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