Editing Quintic function (section)

===''Casus irreducibilis''===

Analogously to [[cubic equation]]s, there are solvable quintics which have five real roots all of whose solutions in radicals involve roots of complex numbers. This is ''[[casus irreducibilis]]'' for the quintic, which is discussed in Dummit.<ref>David S. Dummit [http://www.emba.uvm.edu/~dummit/quintics/solvable.pdf Solving Solvable Quintics]</ref>{{rp|p.17}} Indeed, if an irreducible quintic has all roots real, no root can be expressed purely in terms of real radicals (as is true for all polynomial degrees that are not powers of 2).