John Machin

English mathematician (1686–1751)

For the English nonconformist priest, see John Machin (priest).

John Machin

John Machin

Born| c. 1686[1]

England

Died| 9 June 1751 (aged 70-71)

London, England

Nationality| English
Known for| Machin-like formula
Scientific career
Fields| Mathematician and astronomer
Institutions| Gresham College
Notable students| Brook Taylor

John Machin (bapt. c. 1686 - June 9, 1751)[1] was a professor of astronomy at Gresham College, London. He is best known for developing a quickly converging series for pi in 1706 and using it to compute pi to 100 decimal places.

## History

[edit]

John Machin served as secretary of the Royal Society from 1718 to 1747. He was also a member of the commission which decided the Calculus priority dispute between Leibniz and Newton in 1712.[2]

On 16 May 1713 he succeeded Alexander Torriano as professor of astronomy in Gresham College, and held the post until his death, which occurred in London on 9 June 1751. Machin enjoyed a high mathematical reputation. In 1706, Machin computed the value of π with the formula given below to one hundred decimal places. His ingenious quadrature of the circle was later investigated by Charles Hutton. A mass of his manuscripts is preserved by the Royal Astronomical Society; and writing to William Jones in 1727, he asserted his claim to the parliamentary reward of £10,000 for amending the lunar tables.[2]

In 1728, he was listed as one of the subscribers to the Cyclopaedia of Ephraim Chambers.[3]

## Formula

[edit]

Machin's formula[4] (for which the derivation is straightforward) is:

π 4 = 4 arctan ⁡ 1 5 − arctan ⁡ 1 239 {\displaystyle {\frac {\pi }{4}}=4\arctan {\frac {1}{5}}-\arctan {\frac {1}{239}}}

The benefit of the new formula, a variation on the Gregory–Leibniz series (⁠π/4⁠ = arctan 1), was that it had a significantly increased rate of convergence, which made it a much more practical method of calculation.

To compute π to 100 decimal places, he combined his formula with the Taylor series expansion for the inverse tangent. (Brook Taylor was Machin's contemporary in Cambridge University.) Machin's formula remained the primary tool of pi-hunters for centuries (well into the computer era).

Several other Machin-like formulae are known.

## See also

[edit]

* Gresham Professor of Astronomy

## References

[edit]

Part of a series of articles on the

mathematical constant π
3.1415926535897932384626433...
Uses

* Area of a circle
* Circumference
* Use in other formulae

Properties

* Irrationality
* Transcendence

Value

* Less than 22/7
* Approximations
* Madhava's correction term
* Memorization

People

* Archimedes
* Liu Hui
* Zu Chongzhi
* Aryabhata
* Madhava
* Jamshīd al-Kāshī
* Ludolph van Ceulen
* François Viète
* Seki Takakazu
* Takebe Kenko
* William Jones
* John Machin
* William Shanks
* Srinivasa Ramanujan
* John Wrench
* Chudnovsky brothers
* Yasumasa Kanada

History

* Chronology
* A History of Pi

In culture

* Indiana pi bill
* Pi Day

Related topics

* Squaring the circle
* Basel problem
* Six nines in π
* Other topics related to π

* v
* t
* e

1. ^ a b Anita McConnell, ‘Machin, John (bap. 1686?, died 1751)’, Oxford Dictionary of National Biography, Oxford University Press, 2004. Accessed 26 June 2007. doi:10.1093/ref:odnb/17533
2. ^ a b Clerke 1893.
3. ^ List of Subscribers to the Cyclopaedia Archived 6 October 2020 at the Wayback Machine at library.wisc.edu
4. ^ "Machin's Formula at MathWorld". Archived from the original on 11 July 2019. Retrieved 18 February 2004.

Attribution

* This article incorporates text from a publication now in the public domain: Clerke, Agnes Mary (1893). "Machin, John (d.1751)". In Lee, Sidney (ed.). Dictionary of National Biography. Vol. 35\. London: Smith, Elder & Co.

## External links

[edit]

Works by or about John Machin at Wikisource

* O'Connor, John J.; Robertson, Edmund F., "John Machin", MacTutor History of Mathematics Archive, University of St Andrews
* Media related to John Machin (mathematician) at Wikimedia Commons

* v
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