Matrix’s determinant
Signing:
![]()
singular
Theorem:
, ![]()
Proof: without proof.
Definition:
A and B matrix’s are similar if
T regular : ![]()
Theorem: the similarity is an equivalent relation.
Proof: it comes from the theorem.
Theorem: every square matrix is similar with a triangle one.
Proof: without proof.
Determinant determination:
n=2 :
=![]()
n=3:
=
![]()
We can count it like it because of the permutation.
Theorem:
1.![]()
2.![]()
3.The determinants of similar matrix’s are the same.
Proof:
1. ![]()
2.
, ![]()
![]()
3. ![]()
![]()
Q.E.D.
Determinant of a triangle matrix: the product of the elements in the main counter-diagonal.
La Place endorsement
Definition:
A matrix, then
matrix is created from ‘A’ by leaving its “i” row and “j” column.
Theorem: ![]()
![]()
Proof:
without proof.
![]()
column
![]()
endorsement after the j-th column.
For example:
j=2


For example:
j=1

Adjungated matrix
Definition:
i,j adjungated unit.
Definition:
A adjungated matrix.
For example:



Theorem: A is a regular one (quadratic matrix), then
![]()
Proof:

(theorem)
![]()
a, ![]()
La Place endorsement after the
column.
![]()
b, ![]()
is the same as the determinant of the matrix, created by the changing of the
row to the
row.
and
row are the same
the matrix is a singular one
![]()
, ![]()

3.
/multiplication from left ![]()
/![]()
![]()
Q.E.D
For example:

