Eileen, I do not recall having seen any of the NCTM addendum books on geometry. I do not recall where I learned how, my guess is either from Johnson or Altschiller Court, or maybe from Aref/Wernick. It is a fairly common construction, I think of it through homothetic quadrilaterals.
On Tue, 11 Nov 1997, Eileen M. Klimick Schoaff wrote:
> Isn't the triangle ABC problem with X on AB and Y on AC such that BX = XY = YC > from one of the NCTM Addendum books on geometry? I know I assigned that > problem to my graduate class on teaching geometry last year. The solution is > not at all difficult, just not immediately obvious. > > Eileen Schoaff > Buffalo State College > >