Square Matrices: Invertible, Triangular, Diagonal

This lecture covers the concepts of square matrices, including invertible, triangular, and diagonal matrices. It explains the definitions and properties of square matrices, such as being nxn, invertible if A.A exists, and forming expressions like A.A. It also discusses specific types of matrices, like triangular matrices with zeros above or below the main diagonal, and diagonal matrices with non-zero elements only on the main diagonal.