######## Notation ######## ********** Defined as ********** :math:`\triangleq` means "is defined as". For example, read: .. math:: i \triangleq \sqrt{-1} as "$i$ is defined as the square root of -1." ******* Implies ******* Read $a \implies b$ as "$a$ implies $b$". ************* Biconditional ************* See: `wikipedia on biconditional `_. Read $a \iff b$ as "$a$ if and only if $b$". ************** Set membership ************** :math:`\in` means "in" or "one of". For example: .. math:: k \in 0, 2, 4 means that the value :math:`k` can take any of the three values 0, 2 or 4. :math:`\notin` means "not in" or "not one of". For example: .. math:: k \notin 1, 3, 5 means that the value :math:`k` can *not* take any of the three values 1, 3 or 5, but, all other things being equal, can take any other value. ******* Vectors ******* Read $\vec{v}$ as "vector v". See :doc:`on_vectors`. ************ End of proof ************ Read $\blacksquare$ as "This completes the proof".