# difference between formulas question

• Jun 22nd 2011, 02:11 PM
transgalactic
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?
• Jun 22nd 2011, 02:20 PM
pickslides
Re: difference between formulas question
The first equation is for the diagonalisation. Otherwise consider P^TP = I
• Jun 22nd 2011, 02:22 PM
HallsofIvy
Re: difference between formulas question
If P is orthogonal, $P^T= P^{-1}$ so that those are the same.
• Jun 22nd 2011, 02:25 PM
transgalactic
Re: difference between formulas question
ok ,thanks :)