Special matrices

Summary

• Square matrix: A matrix with dimension \(n×n\) .
• Diagonal elements: The elements \(a_{i,i}\) for \(i=1,...,n\) for a square matrix.
• Diagonal matrix: A square matrix where all off-diagonal elements are zero.
• Identity matrix: A diagonal matrix with \(a_{i,i}=1\)
• Upper triangular matrix: A square matrix with \(a_{i,j}=0\) for \(i>j\)
• Lower triangular matrix: A square matrix with \(a_{i,j}=0\) for \(i<j\)