Complex number->; On the complex plane (equivalent to xy coordinate system)

z = a+bi-& gt； P (a, b)

| z | = (A 2+B 2) (1/2) Pythagorean Theorem

| z | = 1->； Unit circle, | z | = r, general circle (real number with radius of r)

The imaginary part is the 0 (b = 0)- > point on the X-axis.

The real part is 0 (a = 0)->; Points on the y axis.

On the complex plane, z=a+bi equals a vector (starting from (0,0)).

The angle between z and the real axis is φ = arctan (b/a).

Z=z 1+z2 equals vector addition (parallelogram method).