theorem :: BVFUNC_6:82

for Y being non empty set
for a, b, c being Function of Y,BOOLEAN holds a = ((((a 'or' b) 'or' c) '&' ((a 'or' b) 'or' ('not' c))) '&' ((a 'or' ('not' b)) 'or' c)) '&' ((a 'or' ('not' b)) 'or' ('not' c))