Linked from
The 85 pages that link to Complex number, each with the reason it gives.
Complex modulusNarrower topic: The modulus assigns a nonnegative magnitude to every complex number.
Mandelbrot setNarrower topic: The parameter c and every iterated value belong to the complex plane.
Beta functionNarrower topic: The beta function's arguments and values are commonly complex.
Polar formNarrower topic: Polar form is one way to represent this broader kind of number.
Wave mechanicsRelated: Quantum wavefunctions generally take complex values.
Magnitude (mathematics)Related: Its magnitude is the distance from the origin in the complex plane.
Cube rootRelated: Extending cube roots beyond real values introduces multiple complex roots.
Cubic functionRelated: A cubic can have nonreal roots, which occur as a conjugate pair.
Gelfand–Mazur theoremBroader topic: The sole possible algebra is this field with its usual norm.