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## Main Question or Discussion Point

Hello,

The pseudoinverse formula for a matrix A is given by:

P = (A[itex]^{T}[/itex]A)[itex]^{-1}[/itex]A[itex]^{T}[/itex]

I remember knowing this some time ago and this has me worried now....why is (A[itex]^{T}[/itex]A)[itex]^{-1}[/itex] guaranteed to exist? I know it is a square matrix but it could still be degenerate, right?

Would appreciate any help.

Thanks,

Luca

The pseudoinverse formula for a matrix A is given by:

P = (A[itex]^{T}[/itex]A)[itex]^{-1}[/itex]A[itex]^{T}[/itex]

I remember knowing this some time ago and this has me worried now....why is (A[itex]^{T}[/itex]A)[itex]^{-1}[/itex] guaranteed to exist? I know it is a square matrix but it could still be degenerate, right?

Would appreciate any help.

Thanks,

Luca