Complex number

A complex number is a number which contains both an imaginary part and a real part.

Form of a complex number

Complex numbers take this form:

x+yi

This can also rewritten as x+iy and (rarely) yi+x or iy+x.

The real part of a complex number x+yi is x. It is the number without an i term, and is the number we are used to using in everyday maths.

The imaginary part of a complex number x+yi is y. It is the coefficient of i (and the vertical coordinate on an Argand diagram).

Two complex numbers are equal if both their real and imaginary parts are equal.

Question	Answer
Complex number	$ x + yi $ where x is real and y is real; contains a real part and an imaginary part
Real part	x in x+yi, the number without the i term
Imaginary part	y in x+yi, the coefficient of i and the vertical coordinate on an Argand diagram
Equality of complex numbers	Two complex numbers are equal only if both their real parts are equal and their imaginary parts are equal.