theorem receq2d (_G: wff) (z: nat) (_S1 _S2: set) (n: nat): $ _G -> _S1 == _S2 $ > $ _G -> rec z _S1 n = rec z _S2 n $;
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | eqidd | _G -> z = z  | 
        |
| 2 | hyp _h | _G -> _S1 == _S2  | 
        |
| 3 | eqidd | _G -> n = n  | 
        |
| 4 | 1, 2, 3 | receqd | _G -> rec z _S1 n = rec z _S2 n  |