y₂length, x₂length, d-length, & c-length defined (page 2)

bf = y₂length

y₂length can be defined as the y-length of the h-length (segments) from B to A, relative to O.

cf = x₂length

x₂length can be defined as the x-length of the h-length segments from B to A, relative to O.

af = d-length

d-length can be defined as the difference between y-length and y₂length from B to A, relative to O.

ca = c-length

c-length can be defined as the distance between where the h-length (segment) meets BA and where the y-length (segment) meets BA.