The ouguiya spelled "ougiya", is the currency of Mauritania. Each ouguiya constitutes five khoums; as such it is one of two circulating currencies, along with the Malagasy ariary, whose division units are not based on a power of ten. The current ouguiya was introduced in 2018, replacing the old ouguiya at a rate of 1 new ouguiya = 10 old ouguiya, which in turn replaced the CFA franc at a rate of 1 old ouguiya = 5 francs; the name "Ouguiya" is the Hassaniya Arabic pronunciation of "Awqiyyah", meaning "ounce". In 1973, ⅕, 1, 5, 10 and 20 ouguiya coins were introduced into circulation; this was the only year that the khoums was minted, as the ouguiya was worth five CFA Francs a khoums was the equivalent of the franc. The most recent issues were in 2003 and 2004. Coins are minted at the Kremnica mint in Slovakia; the coinage changed in 2009, with a reduced 1 ouguiya in plated composition and a bi-metallic 20 ouguiya issued. A bi-metallic 50 ouguiya was issued December 2010. In 1973, notes were issued by the Central Bank of Mauritania in denominations of 100, 200 and 1,000 ouguiya.
In 1974, a second series of notes was issued in the same denominations, with 500 ouguiya notes added in 1979. Banknotes have been printed by Giesecke & Devrient starting with the second issue. New banknotes were introduced in 2004; these notes have new fronts and the vignettes on the backs have been redesigned to accommodate the reduction in size. The 2,000-ouguiya denomination is new. All but the 100- and 200-ouguiya notes have the denomination expressed in Arabic numerals in a holographic patch at right front; the serial numbers for all denominations now appear horizontally at upper left and lower center, vertically at far right, all formatted with a 2-character prefix, 7-digit serial number, 1-character suffix. An new 5,000-ouguiya denomination dated 28.11.2009 was introduced on 8 August 2010, followed by a redesigned 2,000-ouguiya note dated 28.11.2011 issued on 1 February 2012. Within Nouakchott, the nation's capital, most coins are in fine to fine condition; the Central Bank is unhelpful in providing new condition banknotes.
Some interest in setting up a numismatic program exists, however. On December 5, 2017, the Central Bank of Mauritania announced a redenomination of its currency at a rate of 1:10; as part of the redenomination, a new series of coins were issued in denominations of 1 khoums, 1, 5, 10 and 20 ouguiya, with the latter being struck as a tri-metallic coin and a new series of banknotes in denominations of 50, 100, 200, 500 and 1,000 ouguiya. The new ouguiya banknotes issued for the redenomination are printed in polymer; as a consequence of this change, the ISO Currency Codes for the ouguiya were amended to MRU / 929 and the existing codes of MRO / 478 were retired as per ISO 4217 Amendment Number 165 dated 14 Dec 2017. Economy of Mauritania banknotenews.com
A central bank, reserve bank, or monetary authority is the institution that manages the currency, money supply, interest rates of a state or formal monetary union, oversees their commercial banking system. In contrast to a commercial bank, a central bank possesses a monopoly on increasing the monetary base in the state, generally controls the printing/coining of the national currency, which serves as the state's legal tender. A central bank acts as a lender of last resort to the banking sector during times of financial crisis. Most central banks have supervisory and regulatory powers to ensure the solvency of member institutions, to prevent bank runs, to discourage reckless or fraudulent behavior by member banks. Central banks in most developed nations are institutionally independent from political interference. Still, limited control by the executive and legislative bodies exists. Functions of a central bank may include: implementing monetary policies. Setting the official interest rate – used to manage both inflation and the country's exchange rate – and ensuring that this rate takes effect via a variety of policy mechanisms controlling the nation's entire money supply the Government's banker and the bankers' bank managing the country's foreign exchange and gold reserves and the Government bonds regulating and supervising the banking industry Central banks implement a country's chosen monetary policy.
At the most basic level, monetary policy involves establishing what form of currency the country may have, whether a fiat currency, gold-backed currency, currency board or a currency union. When a country has its own national currency, this involves the issue of some form of standardized currency, a form of promissory note: a promise to exchange the note for "money" under certain circumstances; this was a promise to exchange the money for precious metals in some fixed amount. Now, when many currencies are fiat money, the "promise to pay" consists of the promise to accept that currency to pay for taxes. A central bank may use another country's currency either directly in a currency union, or indirectly on a currency board. In the latter case, exemplified by the Bulgarian National Bank, Hong Kong and Latvia, the local currency is backed at a fixed rate by the central bank's holdings of a foreign currency. Similar to commercial banks, central banks incur liabilities. Central banks create money by issuing interest-free currency notes and selling them to the public in exchange for interest-bearing assets such as government bonds.
When a central bank wishes to purchase more bonds than their respective national governments make available, they may purchase private bonds or assets denominated in foreign currencies. The European Central Bank remits its interest income to the central banks of the member countries of the European Union; the US Federal Reserve remits all its profits to the U. S. Treasury; this income, derived from the power to issue currency, is referred to as seigniorage, belongs to the national government. The state-sanctioned power to create currency is called the Right of Issuance. Throughout history there have been disagreements over this power, since whoever controls the creation of currency controls the seigniorage income; the expression "monetary policy" may refer more narrowly to the interest-rate targets and other active measures undertaken by the monetary authority. Frictional unemployment is the time period between jobs when a worker is searching for, or transitioning from one job to another. Unemployment beyond frictional unemployment is classified as unintended unemployment.
For example, structural unemployment is a form of unemployment resulting from a mismatch between demand in the labour market and the skills and locations of the workers seeking employment. Macroeconomic policy aims to reduce unintended unemployment. Keynes labeled any jobs that would be created by a rise in wage-goods as involuntary unemployment: Men are involuntarily unemployed if, in the event of a small rise in the price of wage-goods to the money-wage, both the aggregate supply of labour willing to work for the current money-wage and the aggregate demand for it at that wage would be greater than the existing volume of employment.—John Maynard Keynes, The General Theory of Employment and Money p11 Inflation is defined either as the devaluation of a currency or equivalently the rise of prices relative to a currency. Since inflation lowers real wages, Keynesians view inflation as the solution to involuntary unemployment. However, "unanticipated" inflation leads to lender losses as the real interest rate will be lower than expected.
Thus, Keynesian monetary policy aims for a steady rate of inflation. A publication from the Austrian School, The Case Against the Fed, argues that the efforts of the central banks to control inflation have been counterproductive. Economic growth can be enhanced by investment such as more or better machinery. A low interest rate implies that firms can borrow money to invest in their capital stock and pay less interest for it. Lowering the interest is therefore considered to encourage economic growth and is used to alleviate times of low economic growth. On the other hand, raising the interest rate is used in times of high economic growth as a contra-cyclical device to keep the economy from overheating and avoid market bubbles. Further goals of monetary policy are stability of interest rates, of the financial market, of the foreign exchange market. Goals cannot be separated fr
São Tomé and Príncipe
São Tomé and Príncipe the Democratic Republic of São Tomé and Príncipe, is an island country in the Gulf of Guinea, off the western equatorial coast of Central Africa. It consists of two archipelagos around the two main islands of São Tomé and Príncipe, about 140 kilometres apart and about 250 and 225 kilometres off the northwestern coast of Gabon, respectively; the islands were uninhabited until their discovery by Portuguese explorers in the 15th century. Colonised and settled by the Portuguese throughout the 16th century, they collectively served as a vital commercial and trade center for the Atlantic slave trade; the rich volcanic soil and close proximity to the Equator made São Tomé and Príncipe ideal for sugar cultivation, followed by cash crops such as coffee and cocoa. Cycles of social unrest and economic instability throughout the 19th and 20th centuries culminated in peaceful independence in 1975. São Tomé and Príncipe has since remained one of Africa's most democratic countries. With a population of 199,910, São Tomé and Príncipe is the second-smallest African sovereign state after Seychelles, as well as the smallest Portuguese-speaking country.
Its people are predominantly with most practising Roman Catholicism. The legacy of Portuguese rule is visible in the country's culture and music, which fuse European and African influences. São Tomé and Príncipe is a founding member state of the Community of Portuguese Language Countries; the islands of São Tomé and Príncipe were uninhabited when the Portuguese arrived sometime around 1470. The islands were discovered by João de Pêro Escobar. Portuguese navigators explored the islands and decided that they would be good locations for bases to trade with the mainland; the dates of discovery are sometimes given as 21 December 1471, for São Tomé. Príncipe was named Santo Antão, changing its name in 1502 to Ilha do Príncipe, in reference to the Prince of Portugal to whom duties on the island's sugar crop were paid; the first successful settlement of São Tomé was established in 1493 by Álvaro Caminha, who received the land as a grant from the crown. Príncipe was settled in 1500 under a similar arrangement.
Attracting settlers proved difficult and most of the earliest inhabitants were "undesirables" sent from Portugal Jews. In time these settlers found the volcanic soil of the region suitable for agriculture the growing of sugar. By 1515, São Tomé and Príncipe had become slave depots for the coastal slave trade centered at Elmina; the cultivation of sugar was a labour-intensive process and the Portuguese began to enslave large numbers of Africans from the mainland. By the mid-16th century the Portuguese settlers had turned the islands into Africa's foremost exporter of sugar. São Tomé and Príncipe were taken over and administered by the Portuguese crown in 1522 and 1573, respectively. However, competition from sugar-producing colonies in the Western Hemisphere began to hurt the islands; the large enslaved population proved difficult to control, with Portugal unable to invest many resources in the effort. Sugar cultivation thus declined over the next 100 years, by the mid-17th century, the economy of São Tomé had changed.
It was now a transit point for ships engaged in the slave trade between the West and continental Africa. In the early 19th century, two new cash crops and cocoa, were introduced; the rich volcanic soils proved well suited to the new cash crop industry, soon extensive plantations, owned by Portuguese companies or absentee landlords, occupied all of the good farmland. By 1908, São Tomé had become the world's largest producer of cocoa, which remains the country's most important crop; the roças system, which gave the plantation managers a high degree of authority, led to abuses against the African farm workers. Although Portugal abolished slavery in 1876, the practice of forced paid labour continued. Scientific American magazine documented in words and pictures the continued use of slaves in São Tomé in its 13 March 1897 issue. In the early 20th century, an internationally publicized controversy arose over charges that Angolan contract workers were being subjected to forced labour and unsatisfactory working conditions.
Sporadic labor unrest and dissatisfaction continued well into the 20th century, culminating in an outbreak of riots in 1953 in which several hundred African laborers were killed in a clash with their Portuguese rulers. This "Batepá Massacre" remains a major event in the colonial history of the islands, its anniversary is observed by the government. By the late 1950s, when other emerging nations across the African Continent demanded their independence, a small group of São Toméans had formed the Movement for the Liberation of São Tomé and Príncipe, which established its base in nearby Gabon. Picking up momentum in the 1960s, events moved after the overthrow of the Caetano dictatorship in Portugal in April 1974; the new Portuguese regime was committed to the dissolution of its overseas colonies. In November 1974, their representatives met with the MLSTP in Algiers and worked out an agreement for the transfer of sovereignty. After a period of transitional government, São Tomé and Príncipe achieved independence on 12 July 1975, choosing as the first president the MLSTP Secretary General
Equatorial Guinea the Republic of Equatorial Guinea, is a country located on the west coast of Central Africa, with an area of 28,000 square kilometres. The colony of Spanish Guinea, its post-independence name evokes its location near both the Equator and the Gulf of Guinea. Equatorial Guinea is the only sovereign African state; as of 2015, the country had an estimated population of 1,222,245. Equatorial Guinea consists of an insular and a mainland region; the insular region consists of the islands of Bioko in the Gulf of Guinea and Annobón, a small volcanic island, the only part of the country south of the equator. Bioko Island is the northernmost part of Equatorial Guinea and is the site of the country's capital, Malabo; the Portuguese speaking island nation of São Tomé and Príncipe is located between Annobón. The mainland region, Río Muni, is bordered by Cameroon on Gabon on the south and east, it is the location of Bata, Equatorial Guinea's largest city, Ciudad de la Paz, the country's planned future capital.
Rio Muni includes several small offshore islands, such as Corisco, Elobey Grande, Elobey Chico. The country is a member of the African Union, Francophonie, OPEC and the CPLP. Since the mid-1990s, Equatorial Guinea has become one of sub-Saharan Africa's largest oil producers, it is the richest country per capita in Africa, its gross domestic product adjusted for purchasing power parity per capita ranks 43rd in the world. The country ranks 135th on the UN's 2016 Human Development Index; the UN says that less than half of the population has access to clean drinking water and that 20% of children die before reaching the age of five. The sovereign state totalitarian government is cited as having one of the worst human rights records in the world ranking among the "worst of the worst" in Freedom House's annual survey of political and civil rights. Reporters Without Borders ranks President Teodoro Obiang Nguema Mbasogo among its "predators" of press freedom. Human trafficking is a significant problem.
S. Trafficking in Persons Report stated that Equatorial Guinea "is a source and destination for women and children subjected to forced labor and forced sex trafficking." The report rates Equatorial Guinea as a government that "does not comply with minimum standards and is not making significant efforts to do so." Pygmies once lived in the continental region, now Equatorial Guinea, but are today found only in isolated pockets in southern Río Muni. Bantu migrations started around 4,000 BP from between south-east Nigeria and north-west Cameroon, they must have settled continental Equatorial Guinea around 2,500 BP at the latest. The earliest settlements on Bioko Island are dated to 1480 BP; the Annobón population native to Angola, was introduced by the Portuguese via São Tomé island. The Portuguese explorer Fernando Pó, seeking a path to India, is credited as being the first European to discover the island of Bioko in 1472, he called it Formosa, but it took on the name of its European discoverer. Fernando Pó and Annobón were colonized by Portugal in 1474.
In 1778, Queen Maria I of Portugal and King Charles III of Spain signed the Treaty of El Pardo which ceded Bioko, adjacent islets, commercial rights to the Bight of Biafra between the Niger and Ogoue rivers to Spain. Spain thereby tried to gain access to a source of slaves controlled by British merchants. Between 1778 and 1810, the territory of Equatorial Guinea was administered by the Viceroyalty of the Río de la Plata, based in Buenos Aires. From 1827 to 1843, the United Kingdom had a base on Bioko to control the slave trade, moved to Sierra Leone under an agreement with Spain in 1843. In 1844, on restoration of Spanish sovereignty, the area became known as the "Territorios Españoles del Golfo de Guinea." Spain had neglected to occupy the large area in the Bight of Biafra to which it had right by treaty, the French had busily expanded their occupation at the expense of the area claimed by Spain. The treaty of Paris in 1900 left Spain with the continental enclave of Rio Muni, a mere 26,000 km2 out of the 300,000 stretching east to the Ubangi river which the Spaniards had claimed.
The plantations of Fernando Pó were run by a black Creole elite known as Fernandinos. The British occupied the island in the early 19th century, settling some 2,000 Sierra Leoneans and freed slaves there. Limited immigration from West Africa and the West Indies continued after the British left. To this were added Cubans and Spaniards of various colours deported for political or other crimes, as well as some assisted settlers. There was a trickle of immigration from the neighbouring Portuguese islands, escaped slaves and prospective planters. Although a few of the Fernandinos were Catholic and Spanish-speaking, about nine-tenths of them were Protestant and English-speaking on the eve of the First World War, pidgin English was the lingua franca of the island; the Sierra Leoneans were well placed as planters while labor recruitment on the Windward coast continued, for they kept family and other connections there and could arrange a supply of labor. The opening years of the twentieth century saw a new generation of Spanish immigrants.
Land regulations issued in 1904–1905 favoured Spaniards
The franc is the currency of Burundi. It is nominally subdivided into 100 centimes, although coins have never been issued in centimes since Burundi began issuing its own currency. Only during the period when Burundi used the Belgian Congo franc were centime coins issued; the franc became the currency of Burundi in 1916, when Belgium occupied the former German colony and replaced the German East African rupie with the Belgian Congo franc. Burundi used the currency of Belgian Congo until 1960, when the Rwanda and Burundi franc was introduced. Burundi began issuing its own francs in 1964. There were plans to introduce a common currency, a new East African shilling, for the five member states of the East African Community by the end of 2015; as of November 2017, these plans have not yet materialized. In 1965, the Bank of the Kingdom of Burundi issued brass 1 franc coins. In 1968, Bank of the Republic of Burundi took over the issuance of coins and introduced aluminum 1 and 5 francs and cupro-nickel 10 francs.
The 5 and 10 francs have continuous milled edges. Second types of the 1 and 5 franc coins were introduced in 1976, featuring the coat of arms. In 2011 new 10 and 50 franc coins were introduced. In 2015 a 100 franc coin was introduced to replace the 100 franc banknote. From February 1964 until 31 December 1965, notes of the Banque d’Emission du Rwanda et du Burundi, in denominations of 5, 10, 20, 50, 100, 500 and 1,000 francs, were overprinted with a diagonal hollow "BURUNDI" for use in the country; these were followed in 1964 and 1965 by regular issues in the same denominations by the Banque du Royaume du Burundi. In 1966, notes for 20 francs and above were overprinted by the Bank of the Republic of Burundi, replacing the word "Kingdom" with "Republic". Regular issues of this bank began in denominations of 20, 50, 100, 500, 1,000 and 5,000 francs. 10 francs were replaced by coins in 1968. 2,000 franc notes were introduced in 2001, followed by 10,000 francs in 2004. Photographer Kelly Fajack's image of school kids in Burundi was used on the back of the Burundian 10,000 franc note.
In 2015 Burundi launched a new series of banknotes. The 10, 20, 50 franc banknotes have lost their legal tender status and the 100 franc banknote has been replaced by a coin during the launch of the new series. On 3 January 2006, the franc was valued at 925 per $1. On January 1, 2008, the franc was valued at 1,129.40 per US dollar. On January 1, 2009, the franc was valued at 1,234.33 per U. S. dollar. On 10 July, the franc was valued at 1,587.60 per US dollar Economy of Burundi
Fixed exchange-rate system
A fixed exchange rate, sometimes called a pegged exchange rate, is a type of exchange rate regime in which a currency's value is fixed against either the value of another single currency, a basket of other currencies, or another measure of value, such as gold. There are risks to using a fixed exchange rate. A fixed exchange rate is used to stabilize the value of a currency by directly fixing its value in a predetermined ratio to a different, more stable, or more internationally prevalent currency to which the value is pegged. In doing so, the exchange rate between the currency and its peg does not change based on market conditions, unlike flexible exchange regime; this makes trade and investments between the two currency areas easier and more predictable and is useful for small economies that borrow in foreign currency and in which external trade forms a large part of their GDP. A fixed exchange-rate system can be used to control the behavior of a currency, such as by limiting rates of inflation.
However, in doing so, the pegged currency is controlled by its reference value. As such, when the reference value rises or falls, it follows that the value of any currencies pegged to it will rise and fall in relation to other currencies and commodities with which the pegged currency can be traded. In other words, a pegged currency is dependent on its reference value to dictate how its current worth is defined at any given time. In addition, according to the Mundell–Fleming model, with perfect capital mobility, a fixed exchange rate prevents a government from using domestic monetary policy to achieve macroeconomic stability. In a fixed exchange-rate system, a country’s central bank uses an open market mechanism and is committed at all times to buy and/or sell its currency at a fixed price in order to maintain its pegged ratio and, the stable value of its currency in relation to the reference to which it is pegged. To maintain a desired exchange rate, the central bank during the devaluation of the domestic money, sells its foreign money in the reserves and buys back the domestic money.
This creates an artificial demand for the domestic money. In case of an undesired appreciation of the domestic money, the central bank buys back the foreign money and thus flushes the domestic money into the market for decreasing the demand and exchange rate; the central bank from its reserves provides the assets and/or the foreign currency or currencies which are needed in order to finance any imbalance of payments. In the 21st century, the currencies associated with large economies do not fix or peg exchange rates to other currencies; the last large economy to use a fixed exchange rate system was the People's Republic of China, which, in July 2005, adopted a more flexible exchange rate system, called a managed exchange rate. The European Exchange Rate Mechanism is used on a temporary basis to establish a final conversion rate against the euro from the local currencies of countries joining the Eurozone; the gold standard or gold exchange standard of fixed exchange rates prevailed from about 1870 to 1914, before which many countries followed bimetallism.
The period between the two world wars was transitory, with the Bretton Woods system emerging as the new fixed exchange rate regime in the aftermath of World War II. It was formed with an intent to rebuild war-ravaged nations after World War II through a series of currency stabilization programs and infrastructure loans; the early 1970's saw the breakdown of the system and its replacement by a mixture of fluctuating and fixed exchange rates. Timeline of the fixed exchange rate system: The earliest establishment of a gold standard was in the United Kingdom in 1821 followed by Australia in 1852 and Canada in 1853. Under this system, the external value of all currencies was denominated in terms of gold with central banks ready to buy and sell unlimited quantities of gold at the fixed price; each central bank maintained gold reserves as their official reserve asset. For example, during the “classical” gold standard period, the U. S. dollar was defined as 0.048 troy oz. of pure gold. Following the Second World War, the Bretton Woods system replaced gold with the U.
S. dollar as the official reserve asset. The regime intended to combine binding legal obligations with multilateral decision-making through the International Monetary Fund; the rules of this system were set forth in the articles of agreement of the IMF and the International Bank for Reconstruction and Development. The system was a monetary order intended to govern currency relations among sovereign states, with the 44 member countries required to establish a parity of their national currencies in terms of the U. S. dollar and to maintain exchange rates within 1% of parity by intervening in their foreign exchange markets. The U. S. dollar was the only currency strong enough to meet the rising demands for international currency transactions, so the United States agreed both to link the dollar to gold at the rate of $35 per ounce of gold and to convert dollars into gold at that price. Due to concerns about America's deteriorating payments situation and massive flight of liquid capital from the U.
S. President Richard Nixon suspended the convertibility of the dollar into gold on 15 August 1971. In December 1971, the Smithsonian Agreement paved the way for the increase in the value of the dollar price of gold from US$35.50 to US$38 an ounce. Speculation against the dollar in March 1973 led to the birth of the independent float, thus terminating the Bretton Woods system. Since March 1973, the floating exchange rate has been followed and formally recognize
A Reuleaux triangle is a shape formed from the intersection of three circular disks, each having its center on the boundary of the other two. Its boundary is a curve of constant width, the simplest and best known such curve other than the circle itself. Constant width means that the separation of every two parallel supporting lines is the same, independent of their orientation; because all its diameters are the same, the Reuleaux triangle is one answer to the question "Other than a circle, what shape can a manhole cover be made so that it cannot fall down through the hole?"Reuleaux triangles have been called spherical triangles, but that term more properly refers to triangles on the curved surface of a sphere. They are named after Franz Reuleaux, a 19th-century German engineer who pioneered the study of machines for translating one type of motion into another, who used Reuleaux triangles in his designs. However, these shapes were known before his time, for instance by the designers of Gothic church windows, by Leonardo da Vinci, who used it for a map projection, by Leonhard Euler in his study of constant-width shapes.
Other applications of the Reuleaux triangle include giving the shape to guitar picks and drill bits for drilling square holes, as well as in graphic design in the shapes of some signs and corporate logos. Among constant-width shapes with a given width, the Reuleaux triangle has the minimum area and the sharpest possible angle at its corners. By several numerical measures it is the farthest from being centrally symmetric, it provides the largest constant-width shape avoiding the points of an integer lattice, is related to the shape of the quadrilateral maximizing the ratio of perimeter to diameter. It can perform a complete rotation within a square while at all times touching all four sides of the square, has the smallest possible area of shapes with this property. However, although it covers most of the square in this rotation process, it fails to cover a small fraction of the square's area, near its corners; because of this property of rotating within a square, the Reuleaux triangle is sometimes known as the Reuleaux rotor.
The Reuleaux triangle is the first of a sequence of Reuleaux polygons, whose boundaries are curves of constant width formed from regular polygons with an odd number of sides. Some of these curves have been used as the shapes of coins; the Reuleaux triangle can be generalized into three dimensions in multiple ways: the Reuleaux tetrahedron does not have constant width, but can be modified by rounding its edges to form the Meissner tetrahedron, which does. Alternatively, the surface of revolution of the Reuleaux triangle has constant width; the Reuleaux triangle may be constructed either directly from three circles, or by rounding the sides of an equilateral triangle. The three-circle construction may be performed with a compass alone, not needing a straightedge. By the Mohr–Mascheroni theorem the same is true more of any compass-and-straightedge construction, but the construction for the Reuleaux triangle is simple; the first step is to mark two arbitrary points of the plane, use the compass to draw a circle centered at one of the marked points, through the other marked point.
Next, one draws a second circle, of the same radius, centered at the other marked point and passing through the first marked point. One draws a third circle, again of the same radius, with its center at one of the two crossing points of the two previous circles, passing through both marked points; the central region in the resulting arrangement of three circles will be a Reuleaux triangle. Alternatively, a Reuleaux triangle may be constructed from an equilateral triangle T by drawing three arcs of circles, each centered at one vertex of T and connecting the other two vertices. Or, equivalently, it may be constructed as the intersection of three disks centered at the vertices of T, with radius equal to the side length of T; the most basic property of the Reuleaux triangle is that it has constant width, meaning that for every pair of parallel supporting lines the two lines have the same Euclidean distance from each other, regardless of the orientation of these lines. In any pair of parallel supporting lines, one of the two lines will touch the triangle at one of its vertices.
The other supporting line may touch the triangle at any point on the opposite arc, their distance equals the radius of this arc. The first mathematician to discover the existence of curves of constant width, to observe that the Reuleaux triangle has constant width, may have been Leonhard Euler. In a paper that he presented in 1771 and published in 1781 entitled De curvis triangularibus, Euler studied curvilinear triangles as well as the curves of constant width, which he called orbiforms. By many different measures, the Reuleaux triangle is one of the most extreme curves of constant width. By the Blaschke–Lebesgue theorem, the Reuleaux triangle has the smallest possible area of any curve of given constant width; this area is 1 2. One method for deriving this area formula is to partition the Reuleaux triangle into an inner equilateral triangle and three curvilinear regions between this inner triangle and the arcs forming the Reuleaux triangle, add the