let Y be non empty set ; :: thesis: for a, b, c being Element of Funcs Y,BOOLEAN holds a 'nand' (b '&' c) = 'not' ((a '&' b) '&' c)
let a, b, c be Element of Funcs Y,BOOLEAN ; :: thesis: a 'nand' (b '&' c) = 'not' ((a '&' b) '&' c)
a 'nand' (b '&' c) = 'not' (a '&' (b '&' c)) by Th1;
hence a 'nand' (b '&' c) = 'not' ((a '&' b) '&' c) by BVFUNC_1:7; :: thesis: verum