FRANCOIS LAVALLOU
64 articles published in Tangente
Math for everyoneN°182May 17, 2018The Gömböc, that obscure object of geometrical desire
An okiagari-koboshi, or Japanese roly-poly toy, is designed always to return to an upright position. This traditional lucky doll symbolizes perseverance—a quality that two Hungarians displayed in abundance when proving the existence of a homogeneous body with the same property.
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History and CultureN°65Jan 06, 2018Linear equations and linear recurrences are one and the same!
One of a mathematician's skills is recognizing the same structures in different guises. A similarity in the calculations used in two ostensibly separate areas is often an early sign of this… Let's look at certain differential equations and sequences.
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Math for everyoneN°64Sep 12, 2017Four authors for one theorem
A tangram consists of seven polygonal pieces that can be assembled to form a given shape. But what about the inverse problem? When can two figures be solutions to the same puzzle? When do they admit the same dissection into elementary shapes? A famous theorem answers that question completely.
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Math for everyoneN°64Sep 11, 2017The Stomachion, the world's oldest puzzle!
The Stomachion is certainly the world's oldest puzzle. It owes its fame not only to Archimedes' interest in it, but also to the extraordinary circumstances in which the Syracusan's writings, lost for two thousand years, were recovered…
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Math for everyoneN°63May 25, 2017Marden's theorem
Complex numbers, born of impossible calculations, found an unlikely geometric interpretation. This meeting of algebra and geometry is beautifully illustrated by theorems about the roots of a complex polynomial.
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Math for everyoneN°63May 23, 2017Complex numbers of modulus 1
Initially mere formal symbols used in algebraic calculations, complex numbers came into widespread use from the 19th century onward thanks to their geometric interpretation... in almost every branch of mathematics! They therefore arise naturally in number theory.
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Math for everyoneN°176May 22, 2017Astounding strophoids
Studied for nearly two centuries before acquiring their final name, strophoids have many interesting properties arising from their similarity under a particular type of transformation. They therefore appear as loci in several classic problems.
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Math for everyoneN°62Feb 14, 2017Formulas for public procurement
Fair competition, which follows from the Declaration of the Rights of Man, is, fortunately, the fundamental principle governing all public procurement. Yet the freedom to choose scoring formulas inevitably introduces an element of subjectivity.
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Math for everyoneN°61Oct 06, 2016Relations and maps: structuring sets
A notion of relation between sets is essential if we are to begin doing mathematics. At the heart of the foundations of mathematics, the concept of a relation includes maps as a special case and gives sets structure.
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History and CultureN°172Sep 12, 2016The "happy ending" problem
In 1933, Hungarian mathematician Eszter Klein posed an apparently elementary geometry problem to a group of young colleagues. It would lead to the birth of a new field of mathematics, discrete geometry, and... a marriage.
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History and CultureN°170May 17, 2016The foundations of differential calculus
A famous scientific quarrel over infinitesimals pitted Rolle against Varignon.
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Math for everyoneN°169Mar 21, 2016Astrological calculations: how consistent are they?
The notion of houses, which originated with the Babylonians, who mainly observed the movements of the stars in the sky as seen from Earth, is an early form of astrology.
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