<j> * <k> = [*((((0 * 0) - (0 * 0)) - (1 * 0)) - (0 * 1)),((((0 * 0) + (0 * 0)) + (1 * 1)) - (0 * 0)),((((0 * 0) + (0 * 1)) + (0 * 0)) - (1 * 0)),((((0 * 1) + (0 * 0)) + (0 * 0)) - (1 * 0))*] by Def9
.= [*0,1,0,0*] ;
hence <j> * <k> = <i> by Lm2, Lm3; :: thesis: verum