A square matrix $A$ is symmetric if:
A$A = -A^T$, the skew-symmetric condition on the chart
B$A^2 = A$, the idempotent condition on the school chart
C$A = A^T$, equal to its own transpose on the school chart
D$AB = BA$ for any matrix $B$ in the school worksheet
Answer & Solution
Correct answer: C. $A = A^T$, equal to its own transpose on the school chart
Symmetric: $A^T = A$.
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