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Exercise 2.2.4

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The matrices that have $A^{+} = A$ are matrices with singular values all equal to 1 or 0, and $u_{i} v_{i}^{T} = v_{i} u_{i}^{T}$ .

If we look at $I = A^{+} A = AA$ , if $A$ is $m$ by $n$ , then we must have $m = n$ to make the multiplication work on the right hand side. So $A$ must be square matrices.

niuers

2020-03-20 00:00

Exercise 2.2.4

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