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Linear Algebra and Its Applications
· Problem 3.3.19
Orthogonality — Gilbert Strang
Mathematics · projection-row-space
Problem
If
P
C
=
A
(
A
T
A
)
−
1
A
T
P_C = A(A^T A)^{-1} A^T
P
C
=
A
(
A
T
A
)
−
1
A
T
is the projection onto the column space of
A
A
A
, what is the projection
P
R
P_R
P
R
onto the row space? (It is not
P
C
T
P_C^T
P
C
T
!)
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