Daniel Lignon
91 articles published in Tangente
Math for everyoneN°90May 07, 2024Free radicals
Being algebraic does not mean being expressible in radicals.
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Math for everyoneN°90May 07, 2024When algebra meets geometry
Some real numbers have a geometric origin: they are defined by straightedge-and-compass constructions. Although the basic idea seems simple, the properties of these numbers are not always easy to establish. This is where algebra proves indispensable.
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Math for everyoneN°90May 06, 2024An astonishing coincidence!
The Borwein brothers, Jonathan (1951–2016) and David (1953–2020), worked extensively on—and published widely about—the number π.
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Math for everyoneN°90May 06, 2024A record
Pi Day is celebrated every year on March 14: in the American date format, this is written 3/14.
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History and CultureN°90May 06, 2024By law, π = 3.2
Well, almost… because the bill did not pass!
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Math for everyoneN°89Feb 19, 2024An unhurried journey to infinity
The harmonic numbers form a sequence that tends to infinity, but very slowly. That does not stop them from playing a role in several important problems.
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Math for everyoneN°89Feb 17, 2024Coming to grips with decimal expansions
Like any real number—for example, pi—a fraction can be written as a finite or infinite decimal expansion. Remarkably, the resulting decimal expansion is always eventually periodic.
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Math for everyoneN°216Feb 13, 2024Essential tools of analysis
Given a somewhat complicated function, who has not wished they could replace it with a much simpler one that "behaves in the same way," such as a polynomial? Taylor expansions make this possible in almost every case—at least locally!
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Math for everyoneN°215Dec 21, 2023PISA: the plunge
Released in December, the results of the 2022 PISA survey (the Programme for International Student Assessment, which assesses 15-year-olds) show a sharp decline in French students’ mathematics performance.
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Math for everyoneN°215Dec 21, 2023Mathematics, the key to the future
More than 180 leading figures from the worlds of science, business and industry warned in the December 5 issue of Le Monde that France is losing ground as a scientific and mathematical power.
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Math for everyoneN°215Dec 21, 2023Inflation: a scam?
Inflation is falling, but prices are rising: are we being lied to? No—sadly, this is normal! Saying that the price index is rising means that "the" function representing prices is increasing.
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Math for everyoneN°213Aug 28, 2023Vauban… for the pigs
Sébastien Le Prestre (1633–1707), Marquis de Vauban, better known simply as Vauban, was an eighteenth-century man of many talents: engineer, military architect, urban planner, encyclopedist… Louis XIV appointed him Marshal of France near the end of his life. He was responsible for numerous military fortresses throughout France.
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