theorem Th39: :: HILBERT3:40

for p, q being Element of HP-WFF
for V being SetValuation
for P being Permutation of V
for x being set st x is_a_fixpoint_of Perm (P,p) holds
for f being Function st f is_a_fixpoint_of Perm (P,(p => q)) holds
f . x is_a_fixpoint_of Perm (P,q)