Review of Complex Number
Definition
Complex number is the combination of real number and imaginary number. It's basic form is a+bi, Where
a is the real part and bi is the imaginary part.
i is the unit for imaginary number. In a complex coordinate, a+bi is point(a,b). The distance between
this point and the origin is <math>sqt(a^2+b^2)</math>.
In the form a+bi, when b=0, the complex number belongs to real number; when a=0, the complex number
belongs to imaginary number; when they both are not zero, it belongs to complex region.
The triangular form of a complex number is Z=r(cosx + isinx). r is the distance between point Z and
the origin on a complex coordiante. rcosx is real part and irsinx is the imaginary part.
