1、 1 1 2 180 3 1 62 2 1 2 3 4 1 O 180 1 2 . 2 1 2 2 AC BD O OA=OC OB=OD OCD O 180 O 180 OAB OCD 180 O O ABC O 180 ABC ABC ABC O AA BB CC O AA ? ? ABC ABC ? (1) O AA (2) ABC ABC (1) A A O 180 OA O 180 OA O A A OA O A O A A O BB CC (2) AOB AOB OA=OA OB OB AOB AOB AOB AOB AB AB BC BC AC AC ABC ABC 3 180
2、4 3 (1) (2) 180 180 1 1 28.2 4 O A O A 2 28.2 5 O ABC O C B A 1 180 2 3 5 1 VWXYZ A 1 B 2 C 3 D 4 2 A 1 B 2 C 3 D 4 3 ABCD EF ED BC G D C D C EFG=55 1= A 55 B 125 C 70 D 110 4 _ 6 . 4 5 _ 1 2 3 4 5 6 6. 26 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 7. ABC C=70 BC=4 AC=4 ABC CB A B C 1 3 ABC A B C 2 x 0 x 4 ABC A B C y y x
