Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

# On Rational Approximations to $\pi+e$: 920/157 Is the 'Best' Rational Approximation to $\pi+e$ with a Denominator of at Most Three Digits

Version 1 : Received: 15 May 2020 / Approved: 16 May 2020 / Online: 16 May 2020 (16:32:49 CEST)
Version 2 : Received: 31 May 2020 / Approved: 31 May 2020 / Online: 31 May 2020 (16:21:52 CEST)

How to cite: Teguia Tabuguia, B. On Rational Approximations to $\pi+e$: 920/157 Is the 'Best' Rational Approximation to $\pi+e$ with a Denominator of at Most Three Digits. Preprints 2020, 2020050268 (doi: 10.20944/preprints202005.0268.v1). Teguia Tabuguia, B. On Rational Approximations to $\pi+e$: 920/157 Is the 'Best' Rational Approximation to $\pi+e$ with a Denominator of at Most Three Digits. Preprints 2020, 2020050268 (doi: 10.20944/preprints202005.0268.v1).

## Abstract

Through the half-unit circle area computation using the integration of the corresponding curve power series representation, we deduce a slow converging positive infinite series to $\pi$. However, by studying the remainder of that series we establish sufficiently close inequalities with equivalent lower and upper bound terms allowing us to estimate, more precisely, how the series approaches $\pi$. We use the obtained inequalities to compute up to four-digit denominator, what are in this sense, the best rational numbers that can replace $\pi$. It turns out that the well-known $22/7$ and $355/113$ called, respectively, Yuel\"{u} and Mil\"{u} in China are the only ones found. This is not so surprising when one considers the empirical computations around these two rational approximations to $\pi$. Thus we apply a similar process to find rational estimations to $\pi+e$ where $e$ is taken as the power series of the exponential function evaluated at $1$. For rational numbers with denominators less than $2000$, $920/157$ turns out to be the only rational number of this type.

## Subject Areas

$\pi$ (read Pi); $e$ (the natural logarithm base); continued fraction; convergent infinite series

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