AB,BC,AB and CA are lines segments on the triangle (AB is the segment from A to B).
D E and F are points on the triangle ABCA, e.g. the point E lies on AB, D on AC and F CB.
the only lengths you are given are:
AB = 7
CD = DE = EF = FC = 1
the only mentioned angle in the challenge is ϑ but you have to figure it out yourself.
you might be getting confused between the points ABCDEF and the variables abcdef which are just numbers (integers I assume) that when throwen into the given function is equal to ϑ
Copyright Open Source Institute, 2006 