[set-theory/en] use not equal ASCII symbol

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Spencer Burris 2021-02-27 18:28:37 -08:00 committed by GitHub
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@ -41,7 +41,7 @@ The cardinality, or size, of a set is determined by the number of items in the s
For example, if `S = { 1, 2, 4 }`, then `|S| = 3`. For example, if `S = { 1, 2, 4 }`, then `|S| = 3`.
### The Empty Set ### The Empty Set
* The empty set can be constructed in set builder notation using impossible conditions, e.g. `∅ = { x : x =/= x }`, or `∅ = { x : x ∈ N, x < 0 }`; * The empty set can be constructed in set builder notation using impossible conditions, e.g. `∅ = { x : x x }`, or `∅ = { x : x ∈ N, x < 0 }`;
* the empty set is always unique (i.e. there is one and only one empty set); * the empty set is always unique (i.e. there is one and only one empty set);
* the empty set is a subset of all sets; * the empty set is a subset of all sets;
* the cardinality of the empty set is 0, i.e. `|∅| = 0`. * the cardinality of the empty set is 0, i.e. `|∅| = 0`.