If A is an orthagonal matrix and B=AP where P is non singular matrix t...
Proof:
Step 1: Show that P is also orthogonal
Since A is orthogonal, we know that:
AA^T = A^TA = I
We can rewrite B as:
B = AP = A(P^T)^T
So, we have:
BB^T = A(P^T)(P^T)^TA^T
Since P is non-singular, we know that P^T is also non-singular. Therefore, we can multiply both sides by (P^T)^-1:
BB^T(P^T)^-1 = AA^T
Since A is orthogonal, we know that AA^T = I. Therefore, we have:
BB^T(P^T)^-1 = I
Multiplying both sides by B^-1, we get:
B^-1BB^T(P^T)^-1 = B^-1
Since B = AP, we can substitute to get:
P^T(A^TA)(P^T)^-1 = B^-1
Simplifying, we get:
P^TP = B^-1
Therefore, we have shown that P is also orthogonal.
Step 2: Show that PB^-1 is orthogonal
We can rewrite PB^-1 as:
PB^-1 = A(P^T)^T(B^-1)^T
Multiplying by its transpose, we get:
(PB^-1)(PB^-1)^T = A(P^T)^T(B^-1)^T(B^-1)(P^T)A^T
Since P is orthogonal, we know that P^T = P^-1. Therefore, we can simplify to get:
(PB^-1)(PB^-1)^T = A(P^-1)(B^-1)(B^-1)(P^-1)A^T
Simplifying, we get:
(PB^-1)(PB^-1)^T = AA^T
Since A is orthogonal, we know that AA^T = I. Therefore, we have:
(PB^-1)(PB^-1)^T = I
Therefore, we have shown that PB^-1 is also orthogonal.