Definition:  for an ordered set of n points ${\text{A}}_{1}\text{,}\text{\hspace{0.17em}}{\text{A}}_{2}\text{,}\text{\hspace{0.17em}}\cdots \text{,}\text{\hspace{0.17em}}{\text{A}}_{n}$, succession of $n1$ straightline segments ${\text{A}}_{\text{1}}{\text{A}}_{\text{2}}\text{,}\text{\hspace{0.17em}}{\text{A}}_{\text{2}}{\text{A}}_{\text{3}}\text{,}\text{\hspace{0.17em}}\cdots \text{,}\text{\hspace{0.17em}}{\text{A}}_{n\text{1}}{\text{A}}_{n}$
