theorem
  |.r*p.| = |.r.|*(sqrt ((p.1)^2+(p.2)^2+(p.3)^2))
proof
  |.r*p.| = |.r.|*|.p.| by EUCLID:11
   .= |.r.|*(sqrt ((p.1)^2+(p.2)^2+(p.3)^2)) by Th56;
  hence thesis;
end;
