Function compositionIn mathematics, function composition is an operation ∘ that takes two functions f and g, and produces a function h = g ∘ f such that h(x) = g(f(x)). In this operation, the function g is applied to the result of applying the function f to x. That is, the functions f : X → Y and g : Y → Z are composed to yield a function that maps x in domain X to g(f(x)) in codomain Z. Intuitively, if z is a function of y, and y is a function of x, then z is a function of x.
Algebraic structureIn mathematics, an algebraic structure consists of a nonempty set A (called the underlying set, carrier set or domain), a collection of operations on A (typically binary operations such as addition and multiplication), and a finite set of identities, known as axioms, that these operations must satisfy. An algebraic structure may be based on other algebraic structures with operations and axioms involving several structures.
Algebraic expressionIn mathematics, an algebraic expression is an expression built up from constant algebraic numbers, variables, and the algebraic operations (addition, subtraction, multiplication, division and exponentiation by an exponent that is a rational number). For example, 3x2 − 2xy + c is an algebraic expression. Since taking the square root is the same as raising to the power 1/2, the following is also an algebraic expression: An algebraic equation is an equation involving only algebraic expressions.
AlgebraAlgebra () is the study of variables and the rules for manipulating these variables in formulas; it is a unifying thread of almost all of mathematics. Elementary algebra deals with the manipulation of variables (commonly represented by Roman letters) as if they were numbers and is therefore essential in all applications of mathematics. Abstract algebra is the name given, mostly in education, to the study of algebraic structures such as groups, rings, and fields.
Algebraic numberAn algebraic number is a number that is a root of a non-zero polynomial in one variable with integer (or, equivalently, rational) coefficients. For example, the golden ratio, , is an algebraic number, because it is a root of the polynomial x^2 − x − 1. That is, it is a value for x for which the polynomial evaluates to zero. As another example, the complex number is algebraic because it is a root of x^4 + 4. All integers and rational numbers are algebraic, as are all roots of integers.
Algebra of setsIn mathematics, the algebra of sets, not to be confused with the mathematical structure of an algebra of sets, defines the properties and laws of sets, the set-theoretic operations of union, intersection, and complementation and the relations of set equality and set inclusion. It also provides systematic procedures for evaluating expressions, and performing calculations, involving these operations and relations.
Boolean algebraIn mathematics and mathematical logic, Boolean algebra is a branch of algebra. It differs from elementary algebra in two ways. First, the values of the variables are the truth values true and false, usually denoted 1 and 0, whereas in elementary algebra the values of the variables are numbers. Second, Boolean algebra uses logical operators such as conjunction (and) denoted as ∧, disjunction (or) denoted as ∨, and the negation (not) denoted as ¬.
2021Like the year 2020, 2021 was also heavily defined by the COVID-19 pandemic, due to the emergence of multiple COVID-19 variants. The major global rollout of COVID-19 vaccines, which began at the end of 2020, continued in 2021. Most major events scheduled for 2020 that were postponed due to the pandemic were hosted in 2021, including the 26th United Nations Climate Change Conference, Expo 2020, and sporting events such as UEFA Euro 2020, the 2020 Summer Olympics and Paralympics, as well as the 2021 Copa América.
FC VSS KošiceFC VSS Košice, formerly 1. FC Košice, was a Slovak football club based in Košice which played in the Slovak 2. Liga during the 2016–17 season. The club officially ceased operations on 27 July 2017. The club, founded in 1903, has won the Slovak League twice, the Slovak Cup five times and the Czechoslovak Cup once. The most successful eras of the club were in the 1970s and 1990s which they spent mostly in the top tier of Czechoslovak and Slovak Football. Two of the UEFA Euro 1976 champions namely Dušan Galis and Jaroslav Pollák played for Košice.
RAF JurbyRoyal Air Force Station Jurby or more simply RAF Jurby is a former Royal Air Force station built in the north west of the Isle of Man. It was opened in 1939 on of land acquired by the Air Ministry in 1937, under the control of No. 29 Group, RAF. During the Second World War the station was used for training as No. 5 Armament Training Station, No. 5 Air Observer School, No. 5 Bombing & Gunnery School and the No. 5 Air Navigation & Bombing School. In addition RAF Jurby also played host to a variety of operational squadrons.
2008–09 Pittsburgh Penguins seasonThe 2008–09 Pittsburgh Penguins season was the 42nd season of Pittsburgh Penguins in the National Hockey League (NHL). The regular season began with two games against the Ottawa Senators in Stockholm, Sweden on October 4 and October 5, 2008. On February 15, the team had a record of 27–25–5 and was five points out of playoff position. The organization fired head coach Michel Therrien and replaced him with Dan Bylsma, head coach of the organization's American Hockey League affiliate in Wilkes-Barre.
9th Cavalry Regiment (United States)The 9th Cavalry Regiment is a parent cavalry regiment of the United States Army. It is not related to the 9th Kansas Cavalry Regiment of the Union Army. Historically, it was one of the Army's four segregated African-American regiments and was part of what was known as the Buffalo Soldiers. The regiment saw combat during the Indian and Spanish–American Wars. During Westward Expansion, the regiment provided escort for the early western settlers and maintained peace on the American frontier.
