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

Let D be an n x n diagonal matrix whose diagonal entries are either 0 or 1

a) Show that D is idempotent

b) Show that if X is a nonsingular matrix and A=XD(X)^{-1}, then A is idempotent

2. Relevant equations

3. The attempt at a solution

a) I tried it, and it works for a specific matrix, say 3x3... but I don't know if it's really a proof.

I need to show that

D^{2}=D

b) I solved this part

Also,

is (AB)^{2}= A^{2}*B^{2}

or

(AB)^{2}=B^{2}*A^{2}

?

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# Homework Help: Linear Algebra- Diagonal Matrix

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