
 S
S s:S. Dec(
s:S. Dec( t:T. f(t) = s)
t:T. f(t) = s) t:T. f(t) = s }
t:T. f(t) = s }
 T
T s:{s:S|
s:{s:S|  t:T. f(t) = s }. f(f@0(s)) = s
t:T. f(t) = s }. f(f@0(s)) = s 
  f1:({s:S|
f1:({s:S|  t:T. f(t) = s }
t:T. f(t) = s }
 (x,y:T//(f(x) = f(y)))). 
Bij({s:S|
(x,y:T//(f(x) = f(y)))). 
Bij({s:S|  t:T. f(t) = s }; x,y:T//(f(x) = f(y)); f1)
t:T. f(t) = s }; x,y:T//(f(x) = f(y)); f1)| 1 |  f@0  {s:S|  t:T. f(t) = s }   (x,y:T//(f(x) = f(y))) | 
| 2 |  Bij({s:S|  t:T. f(t) = s }; x,y:T//(f(x) = f(y)); f@0) | 
| 3 | 9. f1: {s:S|  t:T. f(t) = s }   (x,y:T//(f(x) = f(y)))  Bij({s:S|  t:T. f(t) = s }; x,y:T//(f(x) = f(y)); f1)  Prop | 
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