1. Which topics from calc 3 and linear algebra were a part of today's homework reading?
    1. dot product and cross product
    2. eigenvalues
    3. directional derivative
    4. more than one of the above, but not all
    5. all of the above

U in various places
U x T in 5.1.6
derive of alpha' x U in the information about geodesics on a sphere in 5.1.8

E, F, G,
derivatives of various vectors dotted with U

Shape operator has real eigenvalues. Book reviews material from linear including det, trace, eigevalues, eigenvectors, linear transformation

directional derivative
derivatives of E and F wrt u-directional derivative in the x_u direction