# Matrix

Topics: Matrix, Linear algebra, Vector space Pages: 5 (1347 words) Published: June 12, 2013
In mathematics, a matrix (plural matrices) is a rectangular array of numbers, symbols, or expressions, arranged in rows and columns.[1][2] The individual items in a matrix are called its elements or entries. An example of a matrix with 2 rows and 3 columns is

Matrices of the same size can be added or subtracted element by element. But the rule for matrix multiplication is that two matrices can be multiplied only when the number of columns in the first equals the number of rows in the second. A major application of matrices is to represent linear transformations, that is, generalizations of linear functions such as f(x) = 4x. For example, the rotation of vectors in three dimensional space is a linear transformation. If R is a rotation matrix and v is a column vector (a matrix with only one column) describing the position of a point in space, the product Rv is a column vector describing the position of that point after a rotation. The product of two matrices is a matrix that represents the composition of two linear transformations. Another application of matrices is in the solution of a system of linear equations. If the matrix is square, it is possible to deduce some of its properties by computing its determinant. For example, a square matrix has an inverse if and only if its determinant is not zero. Eigenvalues and eigenvectors provide insight into the geometry of linear transformations. Applications of matrices are found in most scientific fields. In every branch of physics, including classical mechanics, optics, electromagnetism, quantum mechanics, and quantum electrodynamics, they are used to study physical phenomena, such as the motion of rigid bodies. In computer graphics, they are used to project a 3-dimensional image onto a 2-dimensional screen. In probability theory and statistics, stochastic matrices are used to describe sets of probabilities; for instance, they are used within the PageRank algorithm that ranks the pages in a Google search.[3] Matrix calculus generalizes classical analytical notions such as derivatives and exponentials to higher dimensions. A major branch of numerical analysis is devoted to the development of efficient algorithms for matrix computations, a subject that is centuries old and is today an expanding area of research. Matrix decomposition methods simplify computations, both theoretically and practically. Algorithms that are tailored to particular matrix structures, such as sparse matrices and near-diagonal matrices, expedite computations in finite element method and other computations. Infinite matrices occur in planetary theory and in atomic theory. A simple example of an infinite matrix is the matrix representing the derivative operator, which acts on the Taylor series of a function. Contents [hide]

1 Definition
1.1 Size
2 Notation
3 Basic operations
3.1 Addition, scalar multiplication and transposition
3.2 Matrix multiplication
3.3 Row operations
3.4 Submatrix
4 Linear equations
5 Linear transformations
6 Square matrices
6.1 Main types
6.1.1 Diagonal or triangular matrix
6.1.2 Identity matrix
6.1.3 Symmetric or skew-symmetric matrix
6.1.4 Invertible matrix and its inverse
6.1.5 Definite matrix
6.1.6 Orthogonal matrix
6.2 Main operations
6.2.1 Trace
6.2.2 Determinant
6.2.3 Eigenvalues and eigenvectors
7 Computational aspects
8 Decomposition
9 Abstract algebraic aspects and generalizations
9.1 Matrices with more general entries
9.2 Relationship to linear maps
9.3 Matrix groups
9.4 Infinite matrices
9.5 Empty matrices
10 Applications
10.1 Graph theory
10.2 Analysis and geometry
10.3 Probability theory and statistics
10.4 Symmetries and transformations in physics
10.5 Linear combinations of quantum states
10.6 Normal modes
10.7 Geometrical optics
10.8 Electronics
11 History
11.1 Other historical usages of the word “matrix” in mathematics 12 See also
13 Notes
14 References
14.1 Physics references
14.2 Historical references
15 External...