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Gnomon (figure)
In geometry, a gnomon is a plane figure formed by removing a similar parallelogram from a corner of a larger parallelogram; or, more generally, a figure that, added to a given figure, makes a larger figure of the same shape. Building figurate numbers Figurate numbers were a concern of Pythagorean mathematics, and Pythagoras is credited with the notion that these numbers are generated from a ''gnomon'' or basic unit. The gnomon is the piece which needs to be added to a figurate number to transform it to the next bigger one. For example, the gnomon of the square number is the odd number, of the general form 2''n'' + 1, ''n'' = 1, 2, 3, ... . The square of size 8 composed of gnomons looks like this: ~~~~~~~~\begin 8&8&8&8&8&8&8&8\\ 8&7&7&7&7&7&7&7\\ 8&7&6&6&6&6&6&6\\ 8&7&6&5&5&5&5&5\\ 8&7&6&5&4&4&4&4\\ 8&7&6&5&4&3&3&3\\ 8&7&6&5&4&3&2&2\\ 8&7&6&5&4&3&2&1 \end To transform from the ''n-square'' (the square of size ''n'') to the (''n'' + 1)-square, one adjoins 2''n'' + 1 elements: on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnomon
A gnomon (; ) is the part of a sundial that casts a shadow. The term is used for a variety of purposes in mathematics and other fields. History A painted stick dating from 2300 BC that was excavated at the astronomical site of Taosi is the oldest gnomon known in China. The gnomon was widely used in ancient China from the second century BC onward in order to determine the changes in seasons, orientation, and geographical latitude. The ancient Chinese used shadow measurements for creating calendars that are mentioned in several ancient texts. According to the collection of Zhou Chinese poetic anthologies ''Classic of Poetry'', one of the distant ancestors of King Wen of the Zhou dynasty used to measure gnomon shadow lengths to determine the orientation around the 14th century BC. The ancient Greek philosopher Anaximander (610–546 BC) is credited with introducing this Babylonian instrument to the Ancient Greeks. The ancient Greek mathematician and astronomer Oenopides used the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squared Triangular Number
In number theory, the sum of the first cubes is the square of the th triangular number. That is, :1^3+2^3+3^3+\cdots+n^3 = \left(1+2+3+\cdots+n\right)^2. The same equation may be written more compactly using the mathematical notation for summation: :\sum_^n k^3 = \bigg(\sum_^n k\bigg)^2. This identity is sometimes called Nicomachus's theorem, after Nicomachus of Gerasa (c. 60 – c. 120 CE). History Nicomachus, at the end of Chapter 20 of his ''Introduction to Arithmetic'', pointed out that if one writes a list of the odd numbers, the first is the cube of 1, the sum of the next two is the cube of 2, the sum of the next three is the cube of 3, and so on. He does not go further than this, but from this it follows that the sum of the first cubes equals the sum of the first n(n+1)/2 odd numbers, that is, the odd numbers from 1 to n(n+1)-1. The average of these numbers is obviously n(n+1)/2, and there are n(n+1)/2 of them, so their sum is \bigl(n(n+1)/2\bigr)^2. Many early mathem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theo Van Doesburg
Theo van Doesburg (, 30 August 1883 – 7 March 1931) was a Dutch artist, who practiced painting, writing, poetry and architecture. He is best known as the founder and leader of De Stijl. He was married to artist, pianist and choreographer Nelly van Doesburg. Early life Theo van Doesburg was born Christian Emil Marie Küpper on 30 August 1883, in Utrecht, Netherlands, as the son of the photographer and Henrietta Catherina Margadant. After a short period of training in acting and singing, he decided to become a storekeeper. He always regarded his stepfather, Theodorus Doesburg, to be his natural father, so that his first works are signed with Theo Doesburg, to which he later added "van". Career His first exhibition was in 1908. From 1912 onwards, he supported his works by writing for magazines. He considered himself to be a modern painter, at that time, although his early work is in line with the Amsterdam Impressionists and is influenced by Vincent van Gogh, both in style ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dubliners
''Dubliners'' is a collection of fifteen short stories by James Joyce, first published in 1914. It presents a naturalistic depiction of Irish middle class life in and around Dublin in the early years of the 20th century. The stories were written when Irish nationalism was at its peak, and a search for a national identity and purpose was raging; at a crossroads of history and culture, Ireland was jolted by various converging ideas and influences. They centre on Joyce's idea of an epiphany (a moment where a character experiences a life-changing self-understanding or illumination) and the theme of paralysis (Joyce felt Irish nationalism stagnated cultural progression, placing Dublin at the heart of a regressive movement). The first three stories in the collection are narrated by child protagonists, while the subsequent stories are written in the third person and deal with the lives and concerns of progressively older people, in line with Joyce's division of the collection into ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Joyce
James Augustine Aloysius Joyce (2 February 1882 – 13 January 1941) was an Irish novelist, poet, and literary critic. He contributed to the modernist avant-garde movement and is regarded as one of the most influential and important writers of the 20th century. Joyce's novel ''Ulysses'' (1922) is a landmark in which the episodes of Homer's ''Odyssey'' are paralleled in a variety of literary styles, particularly stream of consciousness. Other well-known works are the short-story collection ''Dubliners'' (1914), and the novels ''A Portrait of the Artist as a Young Man'' (1916) and ''Finnegans Wake'' (1939). His other writings include three books of poetry, a play, letters, and occasional journalism. Joyce was born in Dublin into a middle-class family. He attended the Jesuit Clongowes Wood College in County Kildare, then, briefly, the Christian Brothers-run O'Connell School. Despite the chaotic family life imposed by his father's unpredictable finances, he excelled at the Jesuit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Golden Triangle (mathematics)
A golden triangle, also called a sublime triangle, is an isosceles triangle in which the duplicated side is in the golden ratio \varphi to the base side: : = \varphi = \approx 1.618~034~. Angles * The vertex angle is: ::\theta = 2\arcsin = 2\arcsin = 2\arcsin = ~\text = 36^\circ. :Hence the golden triangle is an acute (isosceles) triangle. * Since the angles of a triangle sum to \pi radians, each of the base angles (CBX and CXB) is: ::\beta = ~\text = ~\text = 72^\circ. :Note: ::\beta = \arccos\left(\frac\right)\,\text = ~\text = 72^\circ. * The golden triangle is uniquely identified as the only triangle to have its three angles in the ratio 1 : 2 : 2 (36°, 72°, 72°). In other geometric figures * Golden triangles can be found in the spikes of regular pentagrams. * Golden triangles can also be found in a regular decagon, an equiangular and equilateral ten-sided polygon, by connecting any two adjacent vertices to the center. This is because: 180(10−2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Golden Ratio
In mathematics, two quantities are in the golden ratio if their ratio is the same as the ratio of their sum to the larger of the two quantities. Expressed algebraically, for quantities a and b with a > b > 0, where the Greek letter phi ( or \phi) denotes the golden ratio. The constant \varphi satisfies the quadratic equation \varphi^2 = \varphi + 1 and is an irrational number with a value of The golden ratio was called the extreme and mean ratio by Euclid, and the divine proportion by Luca Pacioli, and also goes by several other names. Mathematicians have studied the golden ratio's properties since antiquity. It is the ratio of a regular pentagon's diagonal to its side and thus appears in the construction of the dodecahedron and icosahedron. A golden rectangle—that is, a rectangle with an aspect ratio of \varphi—may be cut into a square and a smaller rectangle with the same aspect ratio. The golden ratio has been used to analyze the proportions of natural object ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isosceles Triangle
In geometry, an isosceles triangle () is a triangle that has two sides of equal length. Sometimes it is specified as having ''exactly'' two sides of equal length, and sometimes as having ''at least'' two sides of equal length, the latter version thus including the equilateral triangle as a special case. Examples of isosceles triangles include the isosceles right triangle, the golden triangle, and the faces of bipyramids and certain Catalan solids. The mathematical study of isosceles triangles dates back to ancient Egyptian mathematics and Babylonian mathematics. Isosceles triangles have been used as decoration from even earlier times, and appear frequently in architecture and design, for instance in the pediments and gables of buildings. The two equal sides are called the legs and the third side is called the base of the triangle. The other dimensions of the triangle, such as its height, area, and perimeter, can be calculated by simple formulas from the lengths of the legs an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acute Triangle
An acute triangle (or acute-angled triangle) is a triangle with three acute angles (less than 90°). An obtuse triangle (or obtuse-angled triangle) is a triangle with one obtuse angle (greater than 90°) and two acute angles. Since a triangle's angles must sum to 180° in Euclidean geometry, no Euclidean triangle can have more than one obtuse angle. Acute and obtuse triangles are the two different types of oblique triangles — triangles that are not right triangles because they do not have a 90° angle. Properties In all triangles, the centroid—the intersection of the medians, each of which connects a vertex with the midpoint of the opposite side—and the incenter—the center of the circle that is internally tangent to all three sides—are in the interior of the triangle. However, while the orthocenter and the circumcenter are in an acute triangle's interior, they are exterior to an obtuse triangle. The orthocenter is the intersection point of the triangle's t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiplication Table
In mathematics, a multiplication table (sometimes, less formally, a times table) is a mathematical table used to define a multiplication operation for an algebraic system. The decimal multiplication table was traditionally taught as an essential part of elementary arithmetic around the world, as it lays the foundation for arithmetic operations with base-ten numbers. Many educators believe it is necessary to memorize the table up to 9 × 9. History In pre-modern time The oldest known multiplication tables were used by the Babylonians about 4000 years ago. However, they used a base of 60. The oldest known tables using a base of 10 are the Chinese decimal multiplication table on bamboo strips dating to about 305 BC, during China's Warring States period. The multiplication table is sometimes attributed to the ancient Greek mathematician Pythagoras (570–495 BC). It is also called the Table of Pythagoras in many languages (for example French, Italian and Russian), so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geometry
Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is called a ''geometer''. Until the 19th century, geometry was almost exclusively devoted to Euclidean geometry, which includes the notions of point, line, plane, distance, angle, surface, and curve, as fundamental concepts. During the 19th century several discoveries enlarged dramatically the scope of geometry. One of the oldest such discoveries is Carl Friedrich Gauss' ("remarkable theorem") that asserts roughly that the Gaussian curvature of a surface is independent from any specific embedding in a Euclidean space. This implies that surfaces can be studied ''intrinsically'', that is, as stand-alone spaces, and has been expanded into the theory of manifolds and Riemannian geometry. Later in the 19th century, it appeared that geometries ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mathematical Proof
A mathematical proof is an inferential argument for a mathematical statement, showing that the stated assumptions logically guarantee the conclusion. The argument may use other previously established statements, such as theorems; but every proof can, in principle, be constructed using only certain basic or original assumptions known as axioms, along with the accepted rules of inference. Proofs are examples of exhaustive deductive reasoning which establish logical certainty, to be distinguished from empirical arguments or non-exhaustive inductive reasoning which establish "reasonable expectation". Presenting many cases in which the statement holds is not enough for a proof, which must demonstrate that the statement is true in ''all'' possible cases. A proposition that has not been proved but is believed to be true is known as a conjecture, or a hypothesis if frequently used as an assumption for further mathematical work. Proofs employ logic expressed in mathematical symbols ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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