Free implies every subgroup is descendant

Statement
In a free group, every subgroup is a descendant subgroup.

Facts used

 * 1) uses::Free implies residually nilpotent
 * 2) uses::Residually nilpotent implies hypocentral
 * 3) uses::Hypocentral implies every subgroup is descendant

Proof
The proof follows by combining Facts (1)-(3).