1 - week 1 Flashcards
2x3 matrix
has 2 rows and 3 columns
A diagonal matrix
contains only 0’s except for the diagonal (skåt ned gennem matricen)
addition and subtraction
Identity matrix
Has 1’s in the diagonals and 0’s everywhere else
diagonal from the upper left corner to the lower right corner
How to solve a matrix equation?
Matrix multiplication
Hvis matricerne har samme antal rækker og koloner
Husk: du kan kun gange dem sammen hvis de to tal mellem * er ens
(fx A = 2x3, B = 3x1
AB = 3*3)
Inverse of a matrix
How to calculate the inverse of a matrix
From inverse to identity matrix
Notation:
A × A-1 = A-1 × A = I
(Matrix A times inverse of A = Inverse of A times A = Identity Matrix of A)
Skew symetric matrix
AB not equal to BA (concept)
Since A is 4x3 and B is 3x2, it is not possible to multiply the matrices in the order BA
A matrix is symmetric if?
A matrix is symmetric if it is equal to its transpose
A = AT
Before multiplying matrices
Check the dimensions to make sutre they multiply and to check what the new matrix will be
(eg: 2x3)
Multiplying vectors
