JEAN LOUIS LEGRAND
29 articles published in Tangente
Math for everyoneN°72Oct 10, 2019Heilbronn triangles
How should points be placed in a region of the plane to maximize the smallest area determined by any three of them? Despite the elementary nature of this geometry problem, no general solution is known even today!
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Math for everyoneN°71Jul 11, 2019What if our universe were a hologram?
Our universe could be a sphere whose exterior would resemble a black hole. Our world would merely be the reflection of a reality inscribed on the surface of this sphere—a kind of hologram. All information would be encoded on our cosmic horizon. A scenario that may not be so far-fetched after all…
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KnowledgeN°70Apr 11, 2019Round balls
Round, are they? It is not that simple! Each ball is made differently, depending on how it will be used. A survey of their construction offers an opportunity to revisit some lesser-known principles of geometry.
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Math for everyoneN°187Mar 25, 2019The cycloidal pendulum
The cycloidal pendulum has three key properties: it is isochronous, tautochronous and brachistochronous. Behind these learned names lie fundamental properties—so fundamental, in fact, that we owe nothing less than the birth of clockmaking to the pendulum!
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History and CultureN°186Jan 23, 2019Leonardo, inventor of the drone?
Taken together, several studies and inventions foreshadow the advent of drones in aerial photography.
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Math for everyoneN°69Jan 21, 2019When physics “proves”
Some mathematical results are so vivid, so “concrete,” that they lend themselves beautifully to physical experiments. With a little ingenuity, they can even be “proved” physically! This is true of the Pythagorean theorem, the law of cosines and, indeed, triangle geometry as a whole.
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History and CultureN°68Oct 10, 2018Self-driving cars and Hilbert's seventeenth problem
Classical 19th-century mathematics is now joining forces with the latest advances in computational mathematics! In practical terms, rational functions are being enlisted to enable the self-driving cars of the future to travel safely…
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History and CultureN°68Oct 10, 2018Ethical driving
Programming self-driving cars raises ethical questions. Unexpected new conundrums have emerged. Some require only minor adjustments, but others remain unsolvable for now.
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Math for everyoneN°184Sep 25, 2018Calculators in entrance exams: less and less often allowed
For several years now, some written papers in the competitive entrance examinations for France's engineering grandes écoles have prohibited calculators. But this was not a blanket rule.
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Math for everyoneN°67Jun 29, 2018Where do the figures come from?
Public authorities and the media release all kinds of figures, presenting them as indisputable facts. Where do all these numerical data come from? Where can we find them—in online sources, studies or elsewhere? How can we form an informed opinion?
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History and CultureN°67Jun 29, 2018Greenhouse gases: the paradoxes of transport
Greenhouse gas emissions continue to rise. Quantifying the share attributable to road transport is no simple matter—and reducing it is harder still!
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History and CultureN°67Jun 29, 2018The difficult question of forecasting
How can we predict likely changes in temperature and precipitation twenty years, fifty years or a century from now?
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