In what century did prominent Dutch mathematician, Christiaan Huygens, study Tractrix?
Tractrix:  It was first introduced by Claude Perrault in 1670, and later studied by Isaac Newton (1676) and Christiaan Huygens (1692). Christiaan Huygens: Christiaan Huygens, FRS ( or ; ] ) (Latin: "Hugenius" ) (14 April 1629 – 8 July 1695) was a prominent Dutch mathematician and scientist.
1692