Problem bank

Problem 294 of 333HardLinear AlgebraP294

How far a shear stretches

  1. Let

    A=(1101)A = \begin{pmatrix} 1 & 1 \\ 0 & 1 \end{pmatrix}
    • What are the eigenvalues of AA?
    • What is ∥A∥2\|A\|_2, the largest factor by which AA stretches a unit vector, and which unit vector achieves it? What is the condition number of AA?
    • Answer the same for A10A^{10}, and describe how ∥An∥2\|A^n\|_2 grows with nn.

    Why do the eigenvalues give the wrong picture here?