Which of the following is true for the trace of a matrix product ABABAB vs BABABA?
tr(AB)=tr(BA)\text{tr}(AB) = \text{tr}(BA)tr(AB)=tr(BA)
tr(AB)=tr(A)tr(B)\text{tr}(AB) = \text{tr}(A)\text{tr}(B)tr(AB)=tr(A)tr(B)
tr(AB)=0\text{tr}(AB) = 0tr(AB)=0
This only holds if AAA is diagonal