(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Prove that [P]^2=[P] (that the matrix is idempotent)

2. Relevant equations

3. The attempt at a solution

A(A^T*A)^-1 A^T= (A(A^T*A)^-1 A^T)^2

Where A^T is the transpose of A. I have no idea.

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# Homework Help: How to prove that an orthogonal projection matrix is idempotent

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