Lesson 3 · i and square roots of negatives
The imaginary unit iii is the principal square root of −1-1−1: i=−1i = \sqrt{-1}i=−1, i2=−1i^2 = -1i2=−1. For b>0b > 0b>0: −b2=bi\sqrt{-b^2} = bi−b2=bi, and in general −n=in\sqrt{-n} = i\sqrt{n}−n=in.