If \({\rm{A}} = \left[ {\begin{array}{*{20}{c}} {\cos {\rm{\alpha }}}&{\sin {\rm{\alpha }}}\\ { - \sin {\rm{\alpha }}}&{\cos {\rm{\alpha }}} \end{array}} \right]\) then what is AAT equal to (where AT is the transpose of A)?

If \({\rm{A}} = \left[ {\begin{array}{*{20}{c}} {\cos {\rm{\alpha }}}&

1.	If \({\rm{A}} = \left[ {\begin{array}{*{20}{c}} {\cos {\rm{\alpha }}}&{\sin {\rm{\alpha }}}\\ { - \sin {\rm{\alpha }}}&{\cos {\rm{\alpha }}} \end{array}} \right]\) then what is AAT equal to (where AT is the transpose of A)?
A.	Null matrix
B.	Identify matrix
C.	A
D.	-A
Answer» C. A