In the above figure, let 
be the intersection of 
and 
and specify that 
. Then
 |
A beautiful related theorem due to H. Stengel can be stated as follows. In the above figure, let 
lie on the side 
and 
lie on the side 
. Now let 
intersect the line 
at a point 
,
and construct points 
, 
, 
, and 
so that 
. Then
 |
