1. In the homework reading, the following surfaces were not in R3:
    1. Models of hyperbolic geometry
    2. Stereographic projection of the sphere
    3. Flat torus
    4. all of the above
    5. none of the above

    upper half-plane model       conformal, circles and angles



  2. Gauss curvature K is
    1. intrinsic
    2. extrinsic
    3. a vector
    4. both a and c
    5. both b and c