“which remained unknown for 500 years since the inception” Is wrong But an easy way to define the complex plane is to postulate you want multiplication of vec

“which remained unknown for 500 years since the inception” Is wrong But an easy way to define the complex plane is to postulate you want multiplication of vectors in polar form to multiply distance to origin and add angles. No mystery number squares going negative here, just simple and useful geometry ! There’s a whole book about it, Visual Complex Numbers by Tristan Needham. This author is the real boss of the game