# Complex numbers

Level: A Level Maths

A complex number takes the form:

${\displaystyle a+bi}$

Where ${\displaystyle i}$ is the imaginary number ${\displaystyle {\sqrt {-1}}}$, and ${\displaystyle a}$ and ${\displaystyle b}$ are both real numbers.

${\displaystyle a}$ is called the real part of the complex number. ${\displaystyle b}$ is called the imaginary part.

We use the symbol ${\displaystyle \mathbb {C} }$ to represent the complete set of all complex numbers (in a similar way to using ${\displaystyle \mathbb {R} }$ to represent the set of real numbers).