theorem allal (l: nat) {x: nat} (p: wff x):
  $ all {x | p} l <-> A. x (x IN l -> p) $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | bicom | (A. x (x IN l -> p) <-> all {x | p} l) -> (all {x | p} l <-> A. x (x IN l -> p)) | 
        
          | 2 |  | ssab2 | A. x (x e. lmems l -> p) <-> lmems l C_ {x | p} | 
        
          | 3 | 2 | conv all, lmem | A. x (x IN l -> p) <-> all {x | p} l | 
        
          | 4 | 1, 3 | ax_mp | all {x | p} l <-> A. x (x IN l -> p) | 
      
    
    Axiom use
    axs_prop_calc
     (ax_1,
      ax_2,
      ax_3,
      ax_mp,
      itru),
    
axs_pred_calc
     (ax_gen,
      ax_4,
      ax_5,
      ax_6,
      ax_7,
      ax_10,
      ax_11,
      ax_12),
    
axs_set
     (elab,
      ax_8)