Prop
2. Q :
Prop
3. f : {u:
| P(u) }{v:| Q(v) }
4. Inj({u:
| P(u) }; {v:| Q(v) }; f)
5. m : {u:
| P(u) }
6. k : {v:
| Q(v) }
7. (Replace value k by f(m) in f)
{u:| P(u) & 
u = m }{v:| Q(v) & v = k }
8. a1 :
9. P(a1) &
a1 = m
10. a2 :
11. P(a2) &
a2 = m
12. (Replace value k by f(m) in f)(a1) = (Replace value k by f(m) in f)(a2)
13.
f(a1) = k
14.
f(a2) = k
15. f(a1) = f(a2)
a1 = a2 {u:| P(u) & u = m }
