## Complex Numbers and their Properties

Imaginary numbers as we have discussed in Tuesday’s post are numbers of the form bi where $b$ is a real number and $i = \sqrt{-1}$. The term imaginary as (opposed to real) was first used by Rene Descartes, the mathematician who invented Coordinate Geometry — the Cartesian plane in particular.  Leonhard Euler was the one who introduced the symbol $i$ for $\sqrt{-1}$.

Leonhard Euler

Gerolamo Cardano, a pioneer in probability, was the one who suggested the   use of numbers of the form $a + bi$ where $a$ and $b$ are real numbers and $i = \sqrt{-1}$.  Numbers of this form were named complex numbers by Carl Frederich Gauss.The real part of $a + bi$ is $a$ and the imaginary part is bi. » Read more