Salut!
Rezolvarea problemei E3, vă rog.
Mulțumesc!

AO=a/2=OC
DO=b/2=OB
AB=AO=OB=1/2 a + 1/2 b
CB=CO+OB-1/2 a + 1/2 b
CD=CO+OD=-1/2 a -1/2 b
AD=AO+OD=1/2 a - 1/2 b