Mathematics
No, it does have 3 sets of parallel sides though.
No, because equivalent sets are sets that have the SAME cardinality but equal sets are sets that all their elements are precisely the SAME. example: A={a,b,c} and B={1,2,3} equivalent sets C={1,2,3} and D={1,2,3} equal sets
Closure
3,4,5 1,2,3 these are sets of pythagorean triples
In the context of sets, closure implies that the limiting value of the extremum of the set is itself an element of the set.
The concept of closure: If A and B are sets the intersection of sets is a set. Then if the intersection of two sets is a set and that set could be empty but still a set. The same for union, a set A union set Null is a set by closure,and is the set A.
A mixture has multiple sets of chemical properties because it contains different substances with distinct characteristics. Each component of a mixture retains its individual properties, which can affect the overall behavior and properties of the mixture as a whole.
primary dressing, pressure applicator, secondary dressing, and a simple closure
Closures are, interiors not. Proofs are pretty straightforward.
one set
They are closure, associativity, identity and invertibility. A set with addition defined on its elements which meets the above 4 properties becomes a Group.
A cardigan sweater does not have a hood and it has buttons in the front as a closure. Regular sweaters can have buttons or zippers and can also have a hood.
A regular octagon has 4 sets of parallel sides.
For reasons similar to those which explain why mathematicians accept the definition of zero as a number. It provides an identity for unions of sets, provides for closure of sets under taking complements.
geometry
Closure, an identity element, inverse elements, associative property, commutative property