Dynamic components. Please, help

Please. Can someone help me with this dynamic component?

I need to correct my formula so that this trapezoid figure “works” as follows:

I don’t know how to make the edges stay connected in the “?” angle throughout the all movement, from start to finish. I have only been able to get this wrong result:
Edges.skp (442.9 KB)

I will be very grateful to anyone who can help me.

just posted the concept on the original, may wish to delete this post please

¿Cómo puedo eliminar esta publicación?