reserve p,q for Rational;
reserve g,m,m1,m2,n,n1,n2 for Nat;
reserve i,i1,i2,j,j1,j2 for Integer;
reserve R for Ring, F for Field;

theorem Th60:
for R being add-associative right_zeroed right_complementable
            non empty doubleLoopStr,
    a being Element of R holds (-1) '*' a = -a
proof
let R be add-associative right_zeroed right_complementable
         non empty doubleLoopStr,
    a being Element of R;
(-1) '*' a = - (1*a) by Def2 .= - a by BINOM:13;
hence thesis;
end;
