(追記) (追記ここまで)
Polar Form of a Complex Number
The polar coordinates of a complex number on the complex plane. The polar form of a complex number is written in any of the following forms: rcos θ + irsin θ, r(cos θ + isin θ), or rcis θ. In any of these forms r is calledthe modulus or absolute value. θ is called the argument.