You have given a very interesting and easy way to remember the value of “Pi” up to 9 decimals.You solved for “Pi” graphically and got a value of 3.082.

If you solve for “Pi” with analytical geometry,the above construction of Ramanujan gives the value of “Pi” as 355/113 which is 3.141592..This is correct up to 6 decimals. But what is really intriguing is how Ramanujan had

arrived at this approximate construction which a gives value of as 355/113.? Regards

G.Rajamani,Baroda,India

Something called an Erdős–Bacon–Sabbath number has also been devised – this is the sum of your Erdős number, your Bacon number, and your Sabbath number (how many links between you and Black Sabbath in the musical collaboration graph). The current winner (according to this) is Stephen Hawking, with 4+2+2=8.

]]>I remarked earlier today that I think there are only two fixed approximations to \pi that are worth using in practice: 3, and whatever is instantly available in the environment you’re doing sums in – so, for instance, the \pi button on your calculator, or the pre-defined constant you get for ‘pi’ in a more sophisticated calculation environment.

(I note without surprise and with only a touch of sadness that \tau, the manifestly superior circle constant, is not available natively in any calculation environment I am familiar with.)

The joy of following the Biblical approximation is that it is trivial to do sums involving \pi in one’s own head, facilitating estimation. The built-in constant is extremely easy to invoke, almost certain to be free of typographical errors, and likely to have considerably more precision than is required.

There are plenty of situations where neither of those will suffice: but in those situations, you need to think about what is required and make a conscious, informed choice from the wide range of methods available.

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