19.2.1
1.3.::: .2. ...
.
? 1 2..
,,,:(1),?(2). ,,?
. 1 2. 3.O
ABCD A=B=C=D=900ABCD AC = BD AO=CO=BO=DO
ABCO.RtABC, BO= AC
1 ABCDOAOB=60AB=4cm1.AOB2..:(1)ABCD,AC=BD=2AO=2BO() AOB=60 AOB.(2),AB=OA=OBAC=2OA=BD=2OB,AB=4cmAC=BD=8cm
2 ABCD86cm13cm: AOC BOC COD AOD86cm ,AC=BD=13cm()AB+BC+CD+DA=86-2AC+BD=86-413=34cmABCD34cm.
ABCDABC=900AC=AB2+BC2= 32+42= 25=5SABC=1/2ABBC=1/2ACBEBE=ABBC/AC=2.4
1.3cm,120 , _______. 3.ABCDACBDOAB=6BC=8ABO 2. 4cm, 2 cm,________.4. 512 5RtABCCDABDCA=200AB
6.168ABCD7ABCD A98 B196 C280 D284
1 (2) (3)7.2________8.3,ABCDMBCMAMDABCD48cmABCD_______cm2
94-30ABCDAEBDEDAE=3BAECAE
104-31ABCDEFCEEF=CEDE=216AE
: O ABCDOA=OB=OC=ODAOD=1200OBC=300,AOBOA=OB=AB AE BAD,ABCDBAE=DAE=AEB=450AB=BEBEO=BOE=750AOE=AOB+BOE,OAE=OAB-BAEAOE=1350,OAE=150 AOE,AEO=1800-AOE-OAE=300
5ABCBDCEGFBCDEFGDE
?,? ,.
2. ?,? ,.,
:1.:
2.::::P74~P76
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