let K be non empty addLoopStr ; :: thesis: for V, W being non empty VectSpStr of K
for f being Form of V,W
for w being Vector of W holds FunctionalSAF ((- f),w) = - (FunctionalSAF (f,w))
let V, W be non empty VectSpStr of K; :: thesis: for f being Form of V,W
for w being Vector of W holds FunctionalSAF ((- f),w) = - (FunctionalSAF (f,w))
let f be Form of V,W; :: thesis: for w being Vector of W holds FunctionalSAF ((- f),w) = - (FunctionalSAF (f,w))
let w be Vector of W; :: thesis: FunctionalSAF ((- f),w) = - (FunctionalSAF (f,w))

now

let v be Vector of V; :: thesis: (FunctionalSAF ((- f),w)) . v = (- (FunctionalSAF (f,w))) . v
thus (FunctionalSAF ((- f),w)) . v = (- f) . (v,w) by Th10
.= - (f . (v,w)) by Def5
.= - ((FunctionalSAF (f,w)) . v) by Th10
.= (- (FunctionalSAF (f,w))) . v by HAHNBAN1:def 7 ; :: thesis: verum

end;

hence FunctionalSAF ((- f),w) = - (FunctionalSAF (f,w)) by FUNCT_2:113; :: thesis: verum