Determinant

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In algebra, the determinant is a special number associated with any square matrix. The fundamental geometric meaning of a determinant is a scale factor or coefficient for measure when the matrix is regarded as a linear transformation. Thus a 2 × 2 matrix with determinant 2 when applied to a set of points with finite area will transform those points into a set with twice the area. Determinants are important both in calculus, where they enter the substitution rule for several variables, and in multilinear algebra.

When its scalars are taken from a field F, a matrix is invertible if and only if its determinant is nonzero; more generally, when the scalars are taken from a commutative ring R, the matrix is invertible if and only if its determinant is a unit of R. Determinants are not that well-behaved for noncommutative rings.

The determinant of a matrix A is denoted det(A), or without parentheses: det A. An alternative notation, used for compactness, especially in the case where the matrix entries are written out in full, is to denote the determinant of a matrix by surrounding the matrix entries by vertical bars instead of the usual brackets or parentheses. Thus

For a fixed nonnegative integer n, there is a unique determinant function for the n×n matrices over any commutative ring R. In particular, this unique function exists when R is the field of real or complex numbers.

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