- #1
charlies1902
- 162
- 0
Homework Statement
##P=A(A^*A)^{-1}A^*##
where A is a mxn real/complex matrix and ##A^*A## is invertible.
##A^*## means the conjugate transpose of A.
Homework Equations
The Attempt at a Solution
Let y be in the range(A), such that
##y = Ax## for some ##x##.
We can see that ##PA = A(A^*A)^{-1}A^*A = A##
Then
##y = PAx = P(Ax)##
Does this expression above alone show that y is also in the range(P)?