let L be non empty satisfying_Sheffer_1 satisfying_Sheffer_2 satisfying_Sheffer_3 ShefferStr ; :: thesis: for p, x being Element of L holds x = (x | x) | (p | (p | p))

let p, x be Element of L; :: thesis: x = (x | x) | (p | (p | p))

(x | x) | (x | x) = x by SHEFFER1:def 13;

hence x = (x | x) | (p | (p | p)) by SHEFFER1:def 14; :: thesis: verum

let p, x be Element of L; :: thesis: x = (x | x) | (p | (p | p))

(x | x) | (x | x) = x by SHEFFER1:def 13;

hence x = (x | x) | (p | (p | p)) by SHEFFER1:def 14; :: thesis: verum