Imaginary number i concept that everyone in high school contact, but then we only know that it is the square root of -1, but what it really is the meaning of it?
There are a number of axes, there is a red line on the number line, its length it's 1. When it is multiplied by 3 when its length changes, into the blue line, and that when it is multiplied by -1, it becomes a green line, or line of rotation about the origin on the number line 180 degrees.
We know that multiply -1 in fact multiply i twice the line segment is rotated 180 degrees, then once i take it - the answer is simple - rotate 90 degrees.
At the same time, we obtain a vertical imaginary axis. The real axis and the imaginary axis together constitute a complex plane, also called the complex plane. So we learned that Cheng Xu a function of the number of i - rotation.