Since multi-line formatting rarely survives in cyber-space (and is known to be problem-prone on this forum), it is best to use single-line formatting, or else to take advantage of the LaTeX formatting available.
Congruency is often indicated with the "wiggly-equals", simulated on the basic keyboard with the "tilde" (probably near the top left of your keyboard). It would, of course, be wise to define your terms. For instance:
. . . . .By "AB ~ CD", I mean "AB is congruent to CD".
Segments can just be named: "segment AB", for instance.
Eliz.