Final Flashcards
det(Ei(r))
r
det(Eij)
-1
det(Eij(r))
1
det(In)
1
det(ABC…Z)
det(A)det(B)…det(Z)
Determinant of a Triangular/Diagonal Matrix
product of its diagonal matrix
Determinant: Type of matrices
Only square matrices
rank(A) < n
det(A) = 0
no inverse
Determinant of Transpose
= determinant of the original matrix
Cofactor Expansion
Expand along a row or column
-1^(i+j)
Property of Determinant
Can Commute
Adjoint
Cofactor (without first term)
Transpose
A(adj(A)) = det(A)In 1/det(A)(adj(A)) = A^-1
Powers of Matrices
A^k = QD^kQ^-1
Eigenvalue on Triangular Matrix
Entries on diagonal are eigenvalues
det(A-bIn) = 0
Rank Eigenvalues
For a matrix to have an eigenvalue, rank < n
Type of Matrix for Eigenvalues
Square
Characteristic Polynomial
det(A-xIn)
factor to find eigenvalues
Eigenvectors
(A - yIn)X = 0
find basic solution for all eigenvalues (y)
Diagonalizing
Q invertible
QD = AQ
Make eigenvectors of A the columns of Q
D = 0s with eigenvalue diagonal
If A has n distinct eigenvalues,…
Q is invertible
Similar Matrices
A and diagonalized D
- same determinant, eigenvalues and characteristic polynomials
det(A^-1)
1/det(A)
Vector PQ
[q1-p1]
[q2-p2]
Length of a vector
(x^2 + y^2)^(1/2)
Unit vector of v
v/|v|
Dot Product
Multiply terms that are in the same position and add them together.
vwcos(angle)
Dot Product Properties
- distributive over addition
- commutes with scalar multiples
- dot product commutes
Projection
a parallel to w
b perpendicular to w
a = ((v•w)/|w|^2)w = projwV
b = v - a