
theorem :: PMV203: :: PMV(a,b,b) = b;
  for T being _Tree for a, b being Vertex of T holds MiddleVertex(a,b,b) = b
proof
  let T be _Tree;
  let a,b be Vertex of T;
  MiddleVertex(a,b,b) = MiddleVertex(b,a,b) by Th42;
  hence thesis by Th49;
end;
