English
If a reflexive-transitive relation holds from a to b and TransGen r b c holds, then TransGen r a c holds.
Русский
Если ReflTransGen r a b и TransGen r b c, то TransGen r a c.
LaTeX
$$$ \forall {α} {r} {a b c : α}, \mathrm{ReflTransGen} r a b \to \mathrm{TransGen} r b c \to \mathrm{TransGen} r a c $$$
Lean4
theorem trans_right (hab : ReflTransGen r a b) (hbc : TransGen r b c) : TransGen r a c := by
induction hbc with
| single hbc => exact tail' hab hbc
| tail _ hcd hac => exact hac.tail hcd