#f #i1 #i #Hf #f1 #i2 #Hf1 #f2 #H elim (coafter_at_fwd ā¦ Hf ā¦ H) -f
#j1 #H #Hf2 <(at_mono ā¦ Hf1 ā¦ H) -i1 -i2 //
qed-.
lemma coafter_fwd_at1: āi,i2,i1,f,f2. @ā¦i1, fā¦ ā” i ā @ā¦i2, f2ā¦ ā” i ā
#f #i1 #i #Hf #f1 #i2 #Hf1 #f2 #H elim (coafter_at_fwd ā¦ Hf ā¦ H) -f
#j1 #H #Hf2 <(at_mono ā¦ Hf1 ā¦ H) -i1 -i2 //
qed-.
lemma coafter_fwd_at1: āi,i2,i1,f,f2. @ā¦i1, fā¦ ā” i ā @ā¦i2, f2ā¦ ā” i ā