Business I / Eigenvalues and Eigenvectors
Practice question · Multiple choice

A triangular matrix wears its eigenvalues on the diagonal, and a zero among them means the matrix is singular. Why do those two facts fit together?

Hints
  1. Write the determinant of a triangular matrix.
  2. Then write the determinant in terms of the eigenvalues.
Show the answer

A. Because the determinant is the product of the eigenvalues

Why

Both routes give the same number. A zero eigenvalue means some nonzero vector is sent to the origin, the map collapses a direction, which is singularity seen geometrically.

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