Thm_Thm––––––
A∈Mm×n,B∈Mn×pA∈Mm×n,B∈Mn×p
Let AB=[u1u2⋯up],B=[v1v2⋯vp]
Then
uj=Avj,vj=Bej(B=BIp)
Thm_
Let V,W be finite dimensional vector spaces with ordered bases β,γ respectively. Let T be linear. Then
[T(u)]γ=[T]γβ[u]β∀u∈V
Proof_
Let β={v1,⋯,vn},γ={w1,⋯,wm}.
Let [u]β=[a1⋮an]; that is, u=a1v1+⋯+anvn.
[T]γβ=(bij)m×n; that is, T(vj)=n∑i=1bijwi(1≤j≤n).
Then
T(u)=T(n∑j=1ajvj)=n∑j=1ajm∑i=1bijwi=m∑i=1(n∑j=1bijaj)wi
Hence,
[T(u)]γ=[∑nj=1b1jaj⋮∑nj=1bmjaj]=(bij)m×n[a1⋮an]=[T]γβ[u]β
Ex_
Let T:P3(R)→P2(R) be the linear map given by T(f(x))=f′(x).
β={1,x,x2x3},γ={1,x,x2}.
Note
[T]γβ=[010000200003]
Let P(x)=2−4x+x2+3x3; then
[P(x)]β=[2−413],T(P(x))=−4+2x+9x2
so, [T(P(x))]γ=[−429].
On the other hand,
[T]γβ[P(x)]β=[010000200003][2−413]=[−420]
'수학 > 선형대수학' 카테고리의 다른 글
[선형대수학] 가역성, 가역행렬 (Invertibility, Inverse Matrix) (0) | 2020.08.28 |
---|---|
[선형대수학] Left Product Map (0) | 2020.08.27 |
[선형대수학] 행렬의 거듭제곱 (Power of Matrix) (0) | 2020.08.26 |
[선형대수학] 행렬 연산의 성질 (Properties of Matrix Operation) (0) | 2020.08.26 |
[선형대수학] 선형 사상의 합성과 행렬 곱셈 (Compostion of Linear Maps & Matrix Multiplication) (0) | 2020.08.25 |