## Michel Tombroff (BE)

### Pi

##### Texts by Luc Lemaire

The following two sections highlight some of the highlights of this long mathematical history.

### Prelude

Imagine a perfectly spherical planet Earth with a 40,000 kilometre-long equator.  Then imagine placing a rope along the entire equator.

Then cut in one spot and add a meter of rope. If people are placed at every meter of the rope (there are forty million meters) and attempt to lift it as one, how high will they be able to lift it after one meter has been added? (The answer is provided in information level 3.)

Since ancient times, the number π (or pi) has been defined by the relation: p = 2. π.r, where r is the radius of a circle and p its perimeter.

Calculating the exact value of π is not easy. Approximations have been discovered on 4,000-year old Babylonian tablets and on 3,500-year old Egyptian papyrus.

Today, the number of known decimal places (numbers after the period) is 31 trillion and the fascination with such computations is still alive and growing.

Beginning with a simple circle, the number π has gradually spread to every area of mathematics, from the theory of prime numbers and analysis, to infinite sums and probability.

The history of its thorough study, which began with Archimedes, is explained in information level 3.

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