(* Main destructions with ifr ***********************************************)
theorem dfr_des_ifr (f) (p) (q) (t1) (t2): t1 ϵ 𝐓 →
- t1 ➡𝐝𝐟[p,q] t2 → ▼[f]t1 ➡𝐟[⊗p,⊗q] ▼[f]t2.
+ t1 â\9e¡ð\9d\90\9dð\9d\90\9f[p,q] t2 â\86\92 â\96¼[f]t1 â\9e¡ð\9d\90¢ð\9d\90\9f[â\8a\97p,â\8a\97q] â\96¼[f]t2.
#f #p #q #t1 #t2 #H0t1
* #n * #H1n #Ht1 #Ht2
@(ex_intro … (↑♭q)) @and3_intro