1、 1 18 1 2 3 . 1 ( ) 1 2 3 4 5 . 2 6 ( ) 1 ABCD 1= 2 ABCD AB=6cm AC+BD=14cm AOB 3 A B C D AB/CD AB CD BC/AD BC AD ABCD A B C D 4 ABC D E AB AC DE 4 AD 3 AE 2 ABC 3 1. , ABCD , AD ( ) A.4cm B.5cm C.6cm D.8cm 2. , 20cm ABCD O,OE BD AD E, ABE ( ) A.4 cm B.6 cm C.8 cm D.10 cm 3. , ABCD ,AD=5cm,AB BD, O ,
2、OD=2 cm, AB= cm. 4. , ABCD , AC,BD O, O AD,BC M,N, CON 2, DOM 4, AOB . 4 5. , ABCD , AC,BD O, AC=14,BD=8,AB=x, x . 6. , ,O ABCD AC , O AB,CD M,N, E,F MN , OE=OF. (1) ? (2) : MAE= NCF. 1 2 1 ABCD D= , BCD=_ 2. 6 8 A 2 B 14 C 2 14 D 2 12 3 ABCD AB=5 AD=8 BAD ADC BC E F EF= 5 4 a b A D a B C b S ABC=5cm 2 S BCD= 5 ABC D E F ABC DEF 12cm ABC cm 6 ABCD AE BF DAB ABC CD E F AE BF M 1 AE BF 2 DF CE 6
