At: surj is inj gen111121111211111 1. A: Type 2. B: Type 3. f: AB 4. f1: AB 5. g: BA 6. InvFuns(A; B; f1; g) 7. n: 8. f2: nB 9. g1: Bn 10. g1 o f2 = Id 11. f2 o g1 = Id 12. Surj(A; B; f) 13. a1: A 14. a2: A 15. f(a1) = f(a2) 16. g1(f1(a1)) = g1(f1(a2)) 17. f1(a1) = f1(a2) 18. (g o f1)(a1) = (g o f1)(a2)
6. g o f1 = Id 7. f1 o g = Id 8. n: 9. f2: nB 10. g1: Bn 11. g1 o f2 = Id 12. f2 o g1 = Id 13. Surj(A; B; f) 14. a1: A 15. a2: A 16. f(a1) = f(a2) 17. g1(f1(a1)) = g1(f1(a2)) 18. f1(a1) = f1(a2) 19. (g o f1)(a1) = (g o f1)(a2) a1 = a2