Relation Composition and Set Equality
46106
Prove that $D_r \circ D_s = \{ (x,y) \in \mathbb{R}^2 \ | \ |x-y|<r+s \}$, where $D_a = \{ (x,y) \in \mathbb{R}^2\ | \ |x-y| < a \}$
101741
Selection of logical connectives {¬,∨,∧,⇒,⇔} in set theory?
85507
Equivalence Relation problem
122506
Relation on countable sets
22482
How can an ordered pair be expressed as a set?
35362
Number of equivalence relations on a set
56370
Associative operation on a set $S$
65308
Axiom of Choice: Family of non-empty sets mutually disjoint or not?
117479
Mutual set of representatives for left and right cosets: what about infinite groups?
150451
Logic soundness and completeness
3663
Finding counterexamples in elementary set theory.
35577
relations - examples and counterexamples
136284
Orderless pattern matching
83518
Proving Two sets have same cardinality
151561
Proving 'Law of Excluded Middle' in Fitch system
156178
Do counit-unit adjunctions have the expected universal properties?
142886
Find set with maximal cardinality given constraints