Symmetric Matrix

A symmetric matrix is any matrix that is equal to its own transpose: $A=A^T$

These arise for example when represent distances between $i$ and $j$.

Notice that $A{A}^T$ and $A^{T}A$ is symmetric for all matrices $A$. Proof: $(A{A}^T{)}^T=A{A}^T$ $(A^{T}A{)}^T=A^{T}A$

Related

• Skew-Symmetric Matrix