theorem pi222eqd (_G: wff) (_n1 _n2: nat): $ _G -> _n1 = _n2 $ > $ _G -> pi222 _n1 = pi222 _n2 $;
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | hyp _nh | _G -> _n1 = _n2  | 
        |
| 2 | 1 | pi22eqd | _G -> pi22 _n1 = pi22 _n2  | 
        
| 3 | 2 | sndeqd | _G -> snd (pi22 _n1) = snd (pi22 _n2)  | 
        
| 4 | 3 | conv pi222 | _G -> pi222 _n1 = pi222 _n2  |