Equioscillation theorem

In mathematics, the equioscillation theorem concerns the approximation of continuous functions using polynomials when the merit function is the maximum difference (uniform norm).

Its discovery is attributed to Chebyshev.

be a continuous function from

Among all the polynomials of degree

, the polynomial

minimizes the uniform norm of the difference

points

) = σ ( − 1

σ

[1][2] The equioscillation theorem is also valid when polynomials are replaced by rational functions: among all rational functions whose numerator has degree

and denominator has degree

, the rational function

being relatively prime polynomials of degree

n − ν

m − μ

, minimizes the uniform norm of the difference

m + n + 2 − min { μ , ν }

points

) = σ ( − 1

σ

[1] Several minimax approximation algorithms are available, the most common being the Remez algorithm.

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