Much like zero is neither positive nor negative because it sits in the center of the Cartesian plane, why can't it be neither imaginary nor real when it sits in the center of the imaginary plane? According to Wolfram's MathWorld, a purely imaginary number is a complex number z that has no real part, i.e., R[z] = 0.
Ever, who discovered the number I?
Originally coined in the 17th century by René Descartes as a derogatory term and regarded as fictitious or useless, the concept gained wide acceptance following the work of Leonhard Euler (in the 18th century) and Augustin-Louis Cauchy and Carl Friedrich Gauss (in the early 19th century).
Short, who invented complex numbers? Gerolamo Cardano
Different, who invented complex and imaginary numbers?
William Rowan Hamilton
What is I used for in math?
The imaginary unit or unit imaginary number (i) is a solution to the quadratic equation x2 + 1 = 0. Although there is no real number with this property, i can be used to extend the real numbers to what are called complex numbers, using addition and multiplication.