How did imaginary numbers come into existence? What was the first problem that required use of imaginary number?

Question

How did imaginary numbers come into existence? What was the first problem that required use of imaginary number?

In: 760

Answer 1

Rotation. Multiplying with imaginary unit (i) rotates by 90 degrees in 2D complex plane which is very useful because universe is mostly and utterly sinusoidal.