ra119272 ra119272 11-02-2024 Mathematics contestada 2. Is the set {(x, y, z) ∈ R^3 ; z = 0 and x^2 + y^2 ≤ 1} a regular surface? Is the set {(x, y, z) ∈ R^3 ; z = 0, and x^2 + y^2 < 1} a regular surface?