TC … (lex R) ⊆ lex (CTC … R).
#R #HR #L1 #L2 #HL12
lapply (monotonic_TC … (sex cfull (cext2 R) 𝐢) … HL12) -HL12
-[ #L1 #L2 * /3 width=3 by sex_eq_repl_fwd, eq_id_inv_isid/
+[ #L1 #L2 * /3 width=3 by sex_eq_repl_fwd, pr_isi_inv_eq_id/
| /5 width=9 by s_rs_transitive_lex_inv_isid, sex_tc_dx, sex_co, ext2_tc, ex2_intro/
]
qed-.