Jean-Jacques Dupas
107 articles published in Tangente
Math for everyoneN°92Dec 04, 2024The one-cut theorem
Can a polygon be cut from a sheet of paper with a single straight cut? Surprisingly, the answer is yes! More surprisingly still, this also applies to other objects.
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Math for everyoneN°92Dec 03, 2024Inside and outside
How can we systematically determine whether a point lies inside or outside a polygon? Several algorithms, including the "ray-crossing method," solve this problem.
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Math for everyoneN°92Dec 03, 2024The pitfalls of convexity
The word convex comes from the Latin convexus, meaning "rounded". What does this mean mathematically?
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Math for everyoneN°92Dec 03, 2024Regular polygons
Regular polygons are particularly harmonious, thanks to their symmetries. At first glance, one might think they had long since yielded all their secrets. Yet the notion of duality reveals a wealth of surprises.
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Math for everyoneN°92Dec 03, 2024A few constructions
It is always useful to know how to construct the first constructible regular polygons with straightedge and compass. These procedures directly provide methods for calculating the various lengths in the figure.
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History and CultureN°92Dec 03, 2024Albert Girard, the pioneer of classification
The historian of mathematics Siegmund Günther (1848–1923) asserts that Albert Girard of Lorraine (1595–1632) had already given a general definition of the polygon in his 1626 table.
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Math for everyoneN°92Nov 22, 2024What is a polygon?
The definition of a polygon seems intuitive and obvious. Yet when we try to pin down this mathematical object more precisely, several definitions are possible, and the most recent ones may defy common sense.
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Math for everyoneN°92Nov 21, 2024Getting to know quadrilaterals
For the familiar convex quadrilaterals, the classification criteria are, first, whether the sides are parallel, then whether their lengths are equal, and finally whether there are any right angles.
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Math for everyoneN°92Nov 21, 2024All about triangles
Thanks to its simplicity, the triangle is surely the king of polygons. As its name suggests, it has three angles and therefore three sides.
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Math for everyoneN°92Nov 21, 2024How polygons get their names
The word "polygon" comes from the Greek poly, "many", and gonos, "angle, corner", which some authors link to gonou, "knee", the body's archetypal angle.
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InterviewN°92Nov 21, 2024Editorial
When our ancestors settled down, they encountered basic geometric shapes bounded by straight line segments: polygons. The Nile's regular floods thus made it necessary to develop geometric tools for reconstructing the land register, including the shape and area of cultivated fields.
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Math for everyoneN°220Oct 17, 2024The mathematicians of Père-Lachaise
At this time of year, around All Saints’ Day, tradition calls for visits to cemeteries. So let's take the opportunity to visit the graves of mathematicians in the most iconic cemetery of all: Père-Lachaise.
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