Exercise · ZW-ZERMELO-FRAENKEL-AXIOMS-007 · ★★☆ Intermediate
Which of these statements about regularity is correct?
Choose one option.
Show answer
- C. No set can be a member of itself.
Explanation
Regularity excludes a set being a member of itself and, more generally, infinite descending membership chains. The other statements are false in general.
Review the concept: Zermelo–Fraenkel axioms
The Zermelo-Fraenkel axioms (ZF) are the standard axiom system of set theory, formulated in first-order logic. They allow the usual mathematics to be built from the primitive notions of set and membership (\( \in \)).
\[\forall x\,\forall y\,(\forall z\,(z\in x \leftrightarrow z\in y)\rightarrow x=y)\]
More practice problems: zermelo–fraenkel axioms
- ZW-ZERMELO-FRAENKEL-AXIOMS-001 Which of these statements is the axiom of extensionality?
- ZW-ZERMELO-FRAENKEL-AXIOMS-002 What is the name of the axiom that guarantees the existence of \a,b\ for any a and b ?
- ZW-ZERMELO-FRAENKEL-AXIOMS-003 Which axiom guarantees the existence of a set containing the empty set that is closed under success…
- ZW-ZERMELO-FRAENKEL-AXIOMS-004 Which axiom allows forming the set of all subsets of a given set?
- ZW-ZERMELO-FRAENKEL-AXIOMS-005 If A=\1,2\ and B=\3\ , how many elements does A× B have?
- ZW-ZERMELO-FRAENKEL-AXIOMS-006 What is the union of the family \\1\,\1,2\,\2,3\\ ?
- ZW-ZERMELO-FRAENKEL-AXIOMS-008 Which axiom allows defining an image set by applying a formula to a given set?
- ZW-ZERMELO-FRAENKEL-AXIOMS-009 Let A=\∅,\∅\\ . How many elements does P(A) have, and what is correct about A ∈ A under regularity?
← ZW-ZERMELO-FRAENKEL-AXIOMS-006 ZW-ZERMELO-FRAENKEL-AXIOMS-008 →