2.6.2(1) Let A CR be a non – empty set. Refer to Example 2.5.13 for the definition of a greatest element of a set; the definition and properties of a least element of a set are completely analogous....

2.6.2(1)

Please include a formal proof.

Extracted text: 2.6.2(1) Let A CR be a non – empty set. Refer to Example 2.5.13 for the definition of a greatest element of a set; the definition and properties of a least element of a set are completely analogous. (1)Prove that if a € A is a greatest element of A, then A has a least upper bound and lubA = a.