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New pancake series for π

Published online by Cambridge University Press:  18 June 2020

Yannick Saouter*
Affiliation:
655 Avenue du Technopôle, 29200 Plouzané, France e-mail: Yannick.Saouter@imt-atlantique.fr

Extract

In [1], Dalzell proved that $\pi = \frac{{22}}{7} - \int_0^1 {\frac{{{t^4}{{(1 - t)}^4}}}{{1 + {t^2}}}}$ . He then used this equation to derive a new series converging to π. In [2], Backhouse studied the general case of integrals of the form $\int_0^1 {\frac{{{t^m}{{(1 - t)}^m}}}{{1 + {t^2}}}dt}$ and derived conditions on m and n so that they could be used to evaluate π. As a sequel, he derived accurate rational approximations of π. This work was extended in [3] where new rational approximations of π are obtained. Some related integrals of the forms $\int_0^1 {\frac{{{t^m}{{(1 - t)}^m}}}{{1 + {t^2}}}P(t)\,dt}$ and $\int_0^1 {\frac{{{t^m}{{(1 - t)}^m}}}{{\sqrt {1 - {t^2}} }}P(t)dt}$ with P(t) being of polynomial form are also investigated. In [4] the author gives more new approximations and new series for the case m = n = 4k. In [5] new series for π are obtained with the integral $\int_0^a {\frac{{{t^{12m}}{{(a - t)}^{12m}}}}{{1 + {t^2}}}dt}$ where $a = 2 - \sqrt 3$ . The general problem of improving the convergence speed of the arctan series by transformation of the argument has also been considered in [6, 7]. In the present work the author considers an alternative form for the denominators in integrals. As a result, new series are obtained for multiples of π by some algebraic numbers.

Type
Articles
Copyright
© Mathematical Association 2020

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References

Dalzell, D. P., On 22/7, Journal of London Mathematical Society, 19 (1944) pp. 133134.CrossRefGoogle Scholar
Backhouse, N., Pancake functions and approximation to π, Math. Gaz., 79 (July 1995) pp. 371374.CrossRefGoogle Scholar
Lucas, S. K., Integral proofs that 355/113 π, Australian Mathematical Society Gazette, 32(4) (2005) pp. 263266.Google Scholar
Lucas, S. K., Approximations to π derived from integrals with nonnegative integrands, American Mathematical Monthly, 116(2) (2009) pp. 166172.CrossRefGoogle Scholar
Bouey, C. M., Medina, H. M., and Meza, E.. A new series for π via polynomial approximations to arctangent, Involve 5(4) (2012) pp. 421430.CrossRefGoogle Scholar
Scott, J. A.. Another series for the inverse tangent, Math. Gaz., 95 (November 2011) pp. 518520.CrossRefGoogle Scholar
Sofo, A. and Villacorta, J. Cimadevilla, New identities for the arctan function, Journal of Mathematical Analysis, 3(3) (2012) pp. 110.Google Scholar
Euler, L., Investigatio quarundam serierum quae ad rationem peripheriae circuli ad diametrum vero proxime definiendam maxime sunt accommodatae. Nova acta academia scientarum petropolitae, 11 (1798) pp. 150154 available at http://eulerarchive.maa.org/pages/E705.htmlGoogle Scholar