1 2 1. 2. 3. 1. _ 2. ABCD AC BD O AC=10cm BC=8cm ABO _ 3. ? 1. ABCD AC BD O AC=BD ABCD ABCD AB=CD AB CD ABC+ DCB=180 ABC DCB = = = ABC DCB ABC= DCB ABC= ABCD 2. ABCD A= B= C=90 ABCD A+ B+ C+ D= A= B= C=90 D= = = = ABCD ABCD 1. ABCD AB= 6 BC= 8 AC= 10 O D B C A 2 : ABCD 2. ABCD AC BD O AOB AB=4cm, ABC O AC O MN/BC MN BCA E BCA F 1 EO=OF 2 O AECF O D B C A 3 2 1 R P Q S E F A B C O N M D
