I am starting to learn geometrical proofs, and I have come across the Symmetry property of segment congruence (if $AB$ is congruent to $CD$, then $CD$ is congruent to $AB$).
One of the exercises in my book tell me to prove this using the property of reflexivity (segment AB is congruent to segment $AB$), and the theorem that is if segment $AB$ is congruent to segment $CD$ and segment $AB$ is congruent to segment $EF$, then segment $CD$ is congruent to segment $EF$.
I am really stuck and have no idea how to prove this. Please help or give me a starting point.
Thank you.