let Y be non empty set ; :: thesis: for a, b, c being Element of Funcs Y,BOOLEAN holds (a 'imp' b) 'imp' ((a '&' c) 'imp' (b '&' c)) = I_el Y
let a, b, c be Element of Funcs Y,BOOLEAN ; :: thesis: (a 'imp' b) 'imp' ((a '&' c) 'imp' (b '&' c)) = I_el Y
a 'imp' b '<' (a '&' c) 'imp' (b '&' c) by BVFUNC_9:10;
hence (a 'imp' b) 'imp' ((a '&' c) 'imp' (b '&' c)) = I_el Y by BVFUNC_1:19; :: thesis: verum