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arXiv · 1907.04110

Easy Proof of Three Recursive $\pi$-Algorithms -- Einfacher Beweis dreier rekursiver $\pi$-Algorithmen

Lorenz Milla
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Abstract

This paper consists of three independent parts: First we use only elementary algebra to prove that the quartic algorithm of the Borwein brothers has exactly the same output as the Brent-Salamin algorithm, but that the latter needs twice as many iterations. Second we use integral calculus to prove that the Brent-Salamin algorithm approximates $\pi$. Combining these results proves that the Borwein brothers' quartic algorithm also approximates $\pi$. Third, we prove the quadratic convergence of the Brent-Salamin algorithm, which also proves the quartic convergence of Borwein's algorithm. -- -- Dieses Paper besteht aus drei unabh\"angigen Teilen: Erstens beweisen wir mit elementarer Algebra, dass der Borwein-Algorithmus vierter Ordnung die gleichen Ergebnisse liefert wie der Brent-Salamin-Algorithmus, wobei letzterer doppelt so viele Iterationen ben\"otigt. Zweitens beweisen wir mit Integralrechnung, dass der Brent-Salamin-Algorithmus gegen $\pi$ konvergiert. Hieraus folgt, dass der Borwein-Algorithmus vierter Ordnung ebenfalls gegen $\pi$ konvergiert. Drittens beweisen wir die quadratische Konvergenz des Brent-Salamin-Algorithmus und somit auch die quartische Konvergenz des Borwein-Algorithmus.

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BibTeXRIS

Lorenz Milla. 2019-07-09. Easy Proof of Three Recursive $\pi$-Algorithms -- Einfacher Beweis dreier rekursiver $\pi$-Algorithmen. https://arxiv.org/abs/1907.04110

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