This means they are made of both real numbers and the imaginary number i: the square root of negative 1. Remember, a square root of a number represents a number whose square is the original number.

Marcus du Sautoy explains how mathematicians created imaginary numbers by ‘imagining’ the square root of -1. Though imaginary in nature, he then explores how this abstract mathematical idea ...

Mathematicians once turned up their noses at imaginary numbers. But complex analysis actually simplifies math and physics.