. 1 AC ABCD BAC= DCA DAC= BCA AD=BC BAC= DCA DAC= BCA AB DC AB BC ABCD AD=BC 2 ABCD E F G H AB BC CD DA AE=CG BF=DH EG FH EF FG GH HE ABCD AD=BC A= C DH=BF AD-DH=BC-BF AH=CF AEH CGF AE=CG A= C AH=CF AEH CGF HE=FG EF =GH EFGH EG FH 3 E F ABCD AB CD AE=CF DE FB ABCD AB DC EB DF AB=CD AE=CF AB-AE=CD-CF EB=DF EBFD DE FB 4 ABCD B D CD AB E F BE=DF ABCD A= C ABC= CDA BE DF ABC CDA 2= 4= 2 1 ABC 1= 3= 2 1 CDA 1= 2= 3= 4 BED= 4+ C DFB= 3+ A BED= DFB BEDF BE=DF 5 E F ABCD AC AE=CF BF ED BD AC O ABCD OB=OD OA=OC AE=CF OA-AE=OC-CF OE=OF BFDE BF ED
