vault backup: 2026-02-25 08:15:32

timestamped/2025-12-02_10-57-00.md

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+# 2025-12-02 10:57:??
+
+### Set Notation Example
+
+Let $A$ and $B$ be sets
+sharing some but not all elements.
+
+* $A \cap B \neq \varnothing$:
+    "The intersection of $A$ and $B$ is nonempty"
+    (They share at least one element).
+
+* $A \not\subseteq B$:
+    "$A$ is not a subset of $B$"
+    ($A$ has at least one element not in $B$).
+    Equivalent to $A \setminus B \neq \varnothing$.
+
+* $B \not\subseteq A$:
+    "$B$ is not a subset of $A$"
+    ($B$ has at least one element not in $A$).
+    Equivalent to $B \setminus A \neq \varnothing$.