
# Notation¶

## Defined as¶

$$\triangleq$$ means “is defined as”. For example, read:

$i \triangleq \sqrt{-1}$

as “$$i$$ is defined as the square root of -1.”

## Implies¶

Read $$a \implies b$$ as “$$a$$ implies $$b$$”.

## Biconditional¶

Read $$a \iff b$$ as “$$a$$ if and only if $$b$$”.

## Set membership¶

$$\in$$ means “in” or “one of”. For example:

$k \in 0, 2, 4$

means that the value $$k$$ can take any of the three values 0, 2 or 4.

$$\notin$$ means “not in” or “not one of”. For example:

$k \notin 1, 3, 5$

means that the value $$k$$ 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”.

## End of proof¶

Read $$\blacksquare$$ as “This completes the proof”.