# Thread: difference between formulas question

1. ## difference between formulas question

what is the difference between
D=p^-1 A P
and

D=p^t A P

i know then one of them is for diagonalisation of A

what is the purpose of the other?

2. ## Re: difference between formulas question

The first equation is for the diagonalisation. Otherwise consider P^TP = I

3. ## Re: difference between formulas question

If P is orthogonal, $P^T= P^{-1}$ so that those are the same.

ok ,thanks