theorem Th23:
  r*<e3> = |[ 0,0,r ]|
proof
<e3>.1 = 0 & <e3>.2 = 0 & <e3>.3 = 1;
    then r*<e3> = |[ r*0,r*0,r*1 ]| by Lm1 .= |[ 0,0,r ]|;
   hence thesis;
end;
