theorem
  a * LineVec2Mx f =LineVec2Mx (a*f)
proof
A1: len (a*LineVec2Mx f)=len (LineVec2Mx f) by MATRIX_3:def 5;
A2: len (LineVec2Mx f)=1 by MATRIX_0:def 2;
  then Line(a * LineVec2Mx f,1) = a*Line(LineVec2Mx f,1) by MATRIXR1:20
    .= a*f by Th25;
  hence thesis by A2,A1,Th25;
end;
