Interpolation nodes from best uniform approximation

ID: interpolation-nodes-from-best-uniform-approximation

For a real continuous function on a compact interval, choose its best uniform approximation of polynomial degree at most . If its error is nonzero, the Chebyshev alternation theorem supplies ordered alternating extrema. The intermediate value theorem gives a zero of in each intervening interval. At these distinct points, the polynomial interpolant is exactly . If the best error is zero, arbitrary distinct nodes suffice. The Weierstrass approximation theorem shows that these function-dependent interpolants converge uniformly. The nodes depend on the target function; the conclusion does not provide one universal node sequence for every continuous target.

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