%% Title: Logical Symbols Created: 2022-09-15 23:23 Status: Parent: [[Resources/Maths]] Tags: Source: %% # Logical Symbols The basic logical symbols, or *quantifiers*, are the basic notation for mathematics. See also [[Resources/Maths/Symbols|mathematical symbols]], - $\in$: “as in”, or “is a member of” - $\forall$: “for all”; the *universal quantifier*, e.g. $\forall n \in \mathbb{R}: n^2 \geq 0$ - $\exists$: “there exists”; the *existential quantifier* - $\iff$: “if and only if” (or iff) - $\equiv$: “equivalent to”, e.g. $x^3 > 0 \equiv x > 0$ ($x^3$ is positive iff $x$ is positive) - $\implies$: “implies”, e.g. $x > 0 \implies x^2 > 0$. Note that $x^2>0 \implies x>0$ is a false statement, e.g. where $x=-1$. - $\land$: logical and - $\lor$: logical or