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Questions tagged [geometry]

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Old geometry terminology

I was reading Ramsey's 1927 paper "A Contribution to the Theory of Taxation" and came across the following paragraph: "We have $\lambda_1 = \mu_1,\ldots,\lambda_m = \mu_m$, $m$ hyperplanes ($n-1$ ...
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1answer
71 views

Meaning of a cryptic sentence by Gauss on “the mobility of figures in the hyperbolic plane”

G. Waldo Dunnington writes in pages 189-190 of his biography of Gauss: Among the axioms of geometry which do not depend on the parallel postulate are those which secure the free mobility of a ...
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2answers
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What made Euclid/Heron define line as a length without breadth and point as that with no part?

A point is that of which there is no part. And a line is a length without breadth.$^1$ If above definition on point, expresses on point as to be indivisible length, as seems to be expressed in ...
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1answer
117 views

What theorem of Sophus Lie on the number of geometries is H. Poincaré referring to?

In this quotation from Henri Poincaré's essay "Non-Euclidean Geometry" published in Nature in 1892 (No. 1165, Vol 45, p. 406), he refers to a theorem of Sophus Lie. Does anyone know a source for this ...
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2answers
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Who did the drawings in Hilbert's and Cohn-Vossen's “Anschauliche Geometrie”?

Hilbert's and Cohn-Vossen's wonderful book "Anschauliche Geometrie" ("Geometry and the Imagination") from 1932 contains a lot of great illustrations which, given the time of publication, must have ...
3
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1answer
118 views

How - Historically- René Descartes works affect the invention of calculus?

When "Cartesian coordinate system" been discovered By René Descartes, Algebra and Geometry become connected and vice versa , but how that exactly affect Newton and Gottfried Leibniz to invent what we ...
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1answer
146 views

Where does the word ``sine'' (as in $\sin x$) come from?

According to wikipedia (https://en.wikipedia.org/wiki/History_of_trigonometry) : the modern word "sine" is derived from the Latin word sinus, which means "bay", "bosom" or "fold" is indirectly, via ...
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59 views

Does the story about Thales and the heights of pyramids illustrate that Thales did not know of AAA triangle similarity?

Thales understood similar triangles and right triangles, and what is more, used that knowledge in practical ways. The story is told in DL (loc. cit.) that he measured the height of the pyramids by ...
6
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1answer
140 views

How did Eratosthenes determine that Alexandria and Syene were on the same meridian?

As discussed over here, Eratosthenes measured the earth’s circumference by comparing shadows cast at apparent noon at two locations separated by a known distance. Although accounts of the event (like ...
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1answer
86 views

Reference request concerning an alleged Jewish contribution to the early theory of light refraction, and to the first geometry textbook in Europe

Page 50 of the book Gustav Karpeles: A Sketch of Jewish History. Translated from the German [by an anonymous translator]. The Jewish Publication Society of America. 1897. contains the following ...
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1answer
107 views

Origin of arcminutes, arcseconds, “arcthirds,” “arcfourths,” etc

This section of a Wikipedia article says [Modern time and angle notation] contrasts with the numbers used by Hellenistic and Renaissance astronomers, who used thirds, fourths, etc. for finer ...
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141 views

Euclid’s Proposition I.3 overused?

[ Question copied from https://math.stackexchange.com/questions/2541170/euclid-s-proposition-i-3-overused ] Although the references to postulates, axioms, and previous propositions are not part of ...
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1answer
69 views

What geometric results were first proven by assuming all real numbers are rational?

Pythagoras and his followers believed that all magnitudes are commensurable; that is, the ratio of two magnitudes of the same kind, like two lengths or two areas, is equal to the ratio of natural ...
5
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1answer
58 views

What was the old system of using right circular cones to solve problems about circles in the plane?

[I asked this originally at the Math Stack Exchange, and they suggested I also ask about it here.] I heard about this from a college professor but haven't ever been able to find any other mention of ...
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Earliest drawings of the plots of trigonometric functions

[Even though this question may seem as a duplicate of this question about the History of sine function, I'd like to ask it again - with a more specific title and a more specific focus (on specific ...
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1answer
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Centroid in Babylonian Mathematics

Are there any problems in Babylonian mathematics that deal with finding the centroid of some plane figure?
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1answer
80 views

When and why was inversive geometry created/studied?

I have been revisiting math from my highschool through undergrad. I picked Courant’s excellent What is Mathematics? The flow is well so far. However, in one of the chapters he introduces inversion - ...
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What is the purpose of Gauss in his letter to János Bolyai when he mentioned “howling Boeotians”?

I'm wondering what is the purpose of Gauss in his letter to János Bolyai when he mentioned "howling Boeotians"? Is it related to some scientists or philosophers that opposed non-Euclidean geometry? I ...
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How did the integer degrees angles counting being first adopted in geometry and mathematics? [duplicate]

The purpose of this question is trying to know originally how did counting in integer degrees angles from (one degree to $360$ degrees) being adopted basically in geometry, despite the impossibility ...
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2answers
143 views

What mathematical techniques Gauss used in order to tessellate the unit disk?

This question is a continuation of my previously posted question: Was Gauss aware of the non-euclidean implications of his work on moduler forms?, and is based on the information given in John ...
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2answers
343 views

What are the modern connections of the Pentagramma Mirificum studied by Gauss?

In the last years, i read a lot about a mathematical object that was discovered by John Napier in 1620 and explored much more deeply by Gauss, who called this "Pentagramma Mirificum" (latin for "the ...
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1answer
313 views

Sphericity of Earth from lunar eclipses - is Aristotle's argument valid?

Aristotle is often credited with proving the sphericity of Earth from the fact that the shadow of the Earth on the moon during lunar eclipses is always an arc of a round circle (as opposed to arcs of ...
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How old is the Pythagorean Theorem? [closed]

More specifically, what is the oldest evidence of human awareness of what we now call the Pythagorean Theorem? The phrase, "evidence of human awareness" was used to exclude a different question of ...
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100 views

Priority on lemniscate of Gerono?

The Lemniscate of Gerono is a special case of the Lissajous curves. The dates for the two mathematicians are fairly close: Gerono (1799-1891) and Lissajous (1822-1880). Historically who has priority ...
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Indiana Pi Bill: Other attempts to establish mathematical truth by legislative fiat?

Wiki: The Indiana Pi Bill is the popular name for bill #246 of the 1897 sitting of the Indiana General Assembly, one of the most notorious attempts to establish mathematical truth by legislative ...
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1answer
131 views

Was a regular heptagon ever constructed by ancient Greeks?

Today it is well known that a regular heptagon cannot be constructed with straightedge and compass, since it would require to solve an equation of third degree which is not possible with the standard ...
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1answer
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Straightedge and compass

According to most discussions of Euclid's Elements, this work - and indeed, much of Ancient Greek geometry - should be seen as engaged in the game of figuring out what can be done with straightedge ...
3
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1answer
93 views

Who was first to recognize the link between (synthetic) elliptic geometry and geometry on the sphere?

Riemann was the first to talk about elliptic geometry: Bolyai and Lobačevskij (even Gauss too) studied only hyperbolic geometry. But of course some theorems of (planar) elliptic geometry were known ...
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2answers
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Whether Euclid considered squares to be rectangles

When I look up 'that which is right-angled but not equilateral' there are translations that show the word before the above phrase to 'oblong', some that show 'rectangle' and some that show both ...
7
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1answer
139 views

Definitions of continuity pre-Dedekind

In his article on "Kant's Theory of Geometry", Michael Friedman claims that: (...) before Dedekind mathematicians would commonly give what we call the definition of denseness when explaining what ...
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When was this projective property of an ellipse's directrix known?

I stumbled on this image from here: It's mentioned w.r.t. to the elliptical orbits of planets and how the focus-directrix property comes into play. It's an interesting POV but when was such a thing ...
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How was the focus/directrix property of conic sections discovered?

I've always thought that defining conic sections by a locus of points w.r.t the ratio of the distance to the focus and directrix was always "too artificial" - how does one actually discover this ...
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2answers
384 views

What astronomical reason led to the creation of the trigonometric sine and cosine?

Sines and cosines are commonly introduced as ratios of sides of a triangle with its hypotenuse and attributed to ancient Indian scholars. However, I've never actually thought of the reason for ...
3
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1answer
290 views

What is the origin of French/Burmester's curves?

French curves are a set of curvilinear rulers used in industrial design, before the advent of CAD, when everything still had to be drawn by hands. The most popular set of such rulers is made up of 3 ...
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1answer
97 views

Why is there some doubt whether or not Gauss saw the pseudosphere as the embodiment of hyperbolic geometry?

I read a lot of historical articles that doubt the possibility that Gauss saw in the pseudosphere the realization of hyperbolic geometry; that geodetic triangles on the pseudosphere obey the same ...
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3answers
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How was geometry with 3 dimensions discovered/invented?

I wondered if back in the time of ancient Greeks mathematicians, 3D geometry was discovered as result of plane geometry? (Was there anything in the axioms of plane geometry that indicated existence of ...
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1answer
93 views

Has Euclid stated Cauchy's theorem?

Cauchy's Rigidity theorem says that if the corresponding faces of two convex polytopes are isometric (congruent) then the polytopes are related by a (proper or improper) motion. Cauchy's biography (...
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3answers
651 views

How did Aristotle influence Euclid?

In other words, how is Aristotle's logic represented in Euclid's Elements? I have read many articles where Euclid's Elements is linked to Aristotle's logic, but I do not understand, and I can't find ...
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3answers
241 views

What did Lobachevsky do?

It is often said that he discovered non-Euclidean geometry. But in which sense? I am reading the book 'geometry' by Brannan et al. They use the disk model as an example of hyperbolic geometry. Did ...
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2answers
252 views

What topological ideas did Gauss introduce to his student Möbius?

Recently I found a website with good historical information about the contributions of Gauss to Analysis situs (the old term for topology). The site is in German so I made a Google translate to ...
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2answers
293 views

What did Farcas Bolyai write to his son?

There are famous quotes about what Farcas Bolyai wrote to his son Janos to persuade him not to study the "theory of parallels " or what is now known as hyperbolic geometry But not all translation of ...
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1answer
521 views

How did Eratosthenes knew the exact time of the day?

Eratosthenes measured the radius of the Earth with an incredibly accuracy. To do it, you need to measure the length of the shadows from 2 different cities at the same time of the day. Then knowing ...
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2answers
117 views

Is there any evidence supporting this claim about Cassini and his ovals?

The Wikipedia article for Cassini ovals claims in the introduction that "Cassini believed that the Sun traveled around the Earth on one of these ovals, with the Earth at one focus of the oval." This ...
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0answers
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Earliest presentation of a 3-D permutahedron?

Below is a picture of a 3-D permutahedron sundial by Stefano Buonsignori (16th century) in the Medici collection presented by Museo Galileo. The permutahedra / permutohedra and the closely related ...
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2answers
173 views

What exactly did Poincaré mean by 'simply connected'?

I've been reading John Stillwell's translation of the famous Analysis Situs and have become confused about the exact meaning of 'simply connected' in Poincaré's language. On page 7 (in the ...
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3answers
157 views

Who first had the idea to study surfaces via rings of functions, as in algebraic geometry?

This idea provides the foundations of algebraic geometry now; and they have certainly gone down the rabbit hole with it. As a student studying this subject, I have always found it such a great leap to ...
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1answer
172 views

Books or articles criticizing Benoit Mandelbrot? (fractals)

I'm researching about fractals history and one of its main contributor and promoter Benoit Mandelbrot. As far as I'm concerned, when he published his first book about this subject in 1975, he was ...
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1answer
100 views

Origin of the latitude 36 of Eratosthenes

How did Eratosthenes come up with the latitude 36 line, also called 36th parallel north, in the Mediterranean world? Rhodes was one of the navel points in his calculations and even today N36.00 goes ...
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1answer
249 views

A knot cannot be tied in 4-dimensions, but when was this conjectured and proven?

Today it has been shown that a 1-dimensional object in 4-dimensional space cannot be tied into a knot. But I would like to know who first conjectured this and when? And when was it proven? (P.S., is ...
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1answer
154 views

How did the Arabs determine the longitudes of cities?

I am reading the book by Berggren, 'Episodes in the mathematics of medieval islam'. An important problem is determing the direction of Mecca with respect to a local city. The book introduced a method ...