# Definition:Wallis's Number/Historical Note

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## Historical Note on Wallis's Number

The cubic $x^3 - 2 x - 5 = 0$ was used by John Wallis as a example to demonstrate how Newton's Method could be used to solve certain equations numerically.

The real root of this equation has since become known as Wallis's number.

It has subsequently been used as a test for a number of different methods of approximation.

It is known to over $4000$ digits.

## Also see

## Sources

- April 1984: Fred Gruenberger:
*How to handle numbers with thousands of digits, and why one might want to*(*Scientific American***Vol. 250**,*no. 4*: 19 – 26) - 1986: David Wells:
*Curious and Interesting Numbers*... (previous) ... (next): $2 \cdotp 094 \, 551 \ldots$ - 1997: David Wells:
*Curious and Interesting Numbers*(2nd ed.) ... (previous) ... (next): $2 \cdotp 09455 \, 1 \ \ldots$