Original official author HTML, exact retained edition. Historical TeX conversion verdicts remain unchanged. Cited-edition alignment and mathematical self-containment are not assessed.
The section is a nowhere vanishing section
over . Therefore, the function of diagram
(5.13) can be extended to a continuous function on that we also denote . By the definition of the inverse image of a metric, there is a commutative diagram
Then the result is a consequence of the definition of and of the commutativity of the diagram