Example 13. If the diagonals , , of a convex hexagon all bisect the area of the hexagon. Prove: , , are concurrent.
, Polish Mathematical Olympiad)
Solution
Prove that ,
and ,
and ,
thus .
Since they share the same base, then .
Similarly, we can prove that .
Assume intersect at . Consider the homothety centered at that maps to . Since , is the image of under this transformation.
The image of is a line through and parallel to it, and the image of is a line through and parallel to it, so is the common point of these two image lines, thus is the image of point .
Therefore, passes through the homothety center .
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