L8A
      1. Example: Unit Sphere (Method II)
 
L8B
      1. Proposition: The Graph of a Differentiable Function
          Is a Regular Surface
      2. Definition: Critical Points and Critical Values
 
L8C
      1. Definition: Regular Values
      2. Proposition: The Inverse Image of a Regular Value
          Is a Regular Surface
      3. Example: Unit Sphere (Method III)
      4. Recall: Inverse Function Theorem