As shown in the figure, AC ', BD', Ca ', DB' are bisectors of the four inner angles of the planar quadrilateral ABCD Please find out all the parallelograms except for the parallelogram ABCD. No more letters will be added and one of them will be selected to prove that although we didn't learn 5.2 parallelograms from the figure,

As shown in the figure, AC ', BD', Ca ', DB' are bisectors of the four inner angles of the planar quadrilateral ABCD Please find out all the parallelograms except for the parallelogram ABCD. No more letters will be added and one of them will be selected to prove that although we didn't learn 5.2 parallelograms from the figure,

I'm also working on this topic, but it seems that I've done it. I found two parallelograms bb'd'd, parallelograms aa'c'c. I choose parallelograms aa'c'c. I'm going to school. I'll simply write that it's easy to get from the known, aa'parallel c'c. now I just need to prove AC parallel a'c. we can