let R be Ring; :: thesis: for V being RightMod of R
for W1, W2 being Submodule of V holds 0. W1 = 0. W2
let V be RightMod of R; :: thesis: for W1, W2 being Submodule of V holds 0. W1 = 0. W2
let W1, W2 be Submodule of V; :: thesis: 0. W1 = 0. W2
thus 0. W1 = 0. V by Def2
.= 0. W2 by Def2 ; :: thesis: verum