This page covers the determination of eigenvalues and eigenspaces for matrices, focusing on triangular matrices and the characteristic polynomial, defined as the determinant of A−λIn. It...This page covers the determination of eigenvalues and eigenspaces for matrices, focusing on triangular matrices and the characteristic polynomial, defined as the determinant of A−λIn. It explains solving the characteristic polynomial to find eigenvalues, provides examples, and introduces the concept of eigenspaces. It discusses the trace of a matrix and offers recipes for calculating the characteristic polynomial, especially for 2x2 matrices.