Connect FC so that BAE=a and EAD=2a.

∫ The quadrilateral ABCD is a diamond.

∴AB=BC=CD=DA=AE (and parallel)

∴ Angle AEC= 180 degrees -2a

∵ Angle FCE= Angle FAB=a (if you don't believe it, you can prove congruence)

∴ angle EFC= 180 degrees -( 180 degrees-2a)-a = a.

∴EF=EC

∴AE-EF=BC-EC

∴AF=BE

aha

Don't thank me too much.

I am really a good man.

I'm also in Grade Two.

You work harder than me? ! ! !