# Determine if the matrice are orthogonal

• March 12th 2010, 03:02 PM
wopashui
Determine if the matrice are orthogonal
Let A and B be orthogonal nxn matrices. Determine which of the following matrices are orthogonal. (Jusitify)

1) $A^{-1}$ 2) A - B
If AC is also an orthogonal nxn matrix, must C be orthogonal?
• March 13th 2010, 03:00 AM
HallsofIvy
What is the definition of "orthogonal matrix"? Can you use that?