
Weierstrass approximation theorem
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8/9/2026, 8:37:48 PM · Ancient Tree
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Let $f : [a,b] \to \mathbb{R}$ be a [[continuous function|continuous function]] on a [[Closed interval|closed]] bounded interval $[a,b] \subset \mathbb{R}$. Then for every $\varepsilon > 0$, there exists a polynomial $P$ such that
\[
\sup_{x \in [a,b]} |f(x) - P(x)| < \varepsilon.
\]