<Zorn lemma> states that if every <chain in a partially ordered set>[chain] in a nonempty <partially ordered set> has an <upper bound in a partially ordered set>[upper bound] in that set, then the set has a <maximal element>. It is equivalent, over the usual axioms of set theory, to the <axiom of choice>.

Solution

Past exam of the mathematics course of the University of Cambridge / 2020 / ii / Paper 4 / 16H / a / Solution

 Solution (source code)