L27A
       1. Review: Gauss Curvature of a Surface of Revolution 
       2. Derivation: Differential Equation of the Asymptotic Curves
 
L27B
       1. Proposition: The Coordinate Curves Are Asymptotic Curves if and only
           if e=g=0
       2. Example: Asymptotic Curves
 
L27C
       1. Example: Asymptotic Curves (cont.)
       2. Proposition: The Coordinate Curves Are Asymptotic Curves
           if and only if f=F=0