Lagrange theorem demonstrations in GAP with cosets and cardinalities?
117324
How to find all subgroups of a group in GAP
103463
Mantel's Theorem proof verification
130244
Exercise similar to prime avoidance theorem in R.Y. Sharp's textbook
109229
An Example of a Nested Decreasing Sequence of Bounded Closed Sets with Empty Intersection
123613
Double Complement of a set proof
113083
How to prove a set equality?
89506
Union of disjoint sets : Equivalence relations
71159
Example of Erdos-Szekeres bound being tight
41726
Musical and combinatorial proof
39382
Examples of the Pigeonhole Principle
83518
Proving Two sets have same cardinality
59644
Proof of Cartesian product intersection
113922
Proof that the intersection of any finite number of convex sets is a convex set
157079
Maximal cardinality of a family of pairwise disjoint "figure eights" in the plane
134440
An unexpected application of non-trivial combinatorics
55259
ArcTan[z] and ArcTan[x,y], Restriction and Conversion
142631
Show that A has the same cardinality as $A\setminus\{x,y,z\}$