theorem Th65:
  0.R <> 1_R & {v1,v2} is linearly-independent implies v1 <> 0.V & v2 <> 0.V
proof
A1: v1 in {v1,v2} & v2 in {v1,v2} by TARSKI:def 2;
  assume 0.R <> 1_R & {v1,v2} is linearly-independent;
  hence thesis by A1,Th63;
end;
