arXiv subjects
Publications and source records attributed to Juan Tolosa.
We study directions along which the norms of vectors are preserved under a linear map. In particular, we find families of matrices for which these directions are determined by integer vectors. We consider the two-dimensional case in detail, and also discuss the extension to the three-dimensional case.
Starting from a mistake done by a student, we discover an unexpected method of finding both eigenvectors for a $2\times2$ matrix with distinct eigenvalues in a single computation. We discuss a connection with the Cayley-Hamilton theorem, and show the corresponding generalization for a $3 \times 3$ matrix. The arguments should be understandable for strong linear algebra students.