theorem Th26:
  dist(r*p,r*q) = |.r.|*dist(p,q)
proof
  thus dist(r*p,r*q) = dist(r*p-r*p,r*p-r*q) by Th25
    .= dist(|[0,0]|,r*p-r*q) by EUCLID:54,RLVECT_1:5
    .= dist(|[0,0]|,r*(p-q)) by RLVECT_1:34
    .= |.r.|*dist(|[0,0]|,p-q) by Th20
    .= |.r.|*dist(p-p,p-q) by EUCLID:54,RLVECT_1:5
    .= |.r.|*dist(p,q) by Th25;
end;
