Operations
with Matrices
- Two matrix A and B are equal if, and only if, they are both of the same shape m × n and corresponding elements are equal.
- Two matrix A and B can be added (or subtracted) of, and only if, they have the same shape m × n . If
- If k is a scalar, and A = ⌊ aij ⌋ is a matrix, then
- Multiplication of Two Matrices
Two matrices can be
multiplied together only when the number of column in the first is equal to the
number of rows in the second If
- Transpose of a Matrix
If the rows and columns
of a matrix are interchanged, then the new matrix is called the transpose of the original matrix. If A is
the original matrix, its transpose is denoted AT or
Ã.
- If the matrix product AB is defined, then (AB)T = BT AT.
- Adjoint of Matrix
If A is a square n
× n matrix, its adjoint, denated by adj A, is the transpose
of the matrix of cofactors Cij of A: adj A = [Cij]T.
- Trace of a Matrix
If A is a square n
× n matrix, its trace, denated by tr A, is defined to be
the sum of the terms on the leading diagonal: tr A = a11 +
a22 + … + ann.
- Inverse of a Matrix
If A is a square n
× n matrix with a nonsingular
determinant det A, then its inverse A–
1 is given by
- If the matrix product AB is defined, then (AB)– 1 = B – 1 A – 1 .
- If A is a square n × n matrix, the eigenvectors X satisfy the equation
AX = λX,
While the eigenvalues λ
satisfy the characteristic equation | A – λ I | = 0.
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