1、 1 1 FE CD 2=26 1= AB CD 2 AB CD CM BCD 74 B CM CN NCE _ 3 AD CAB DE AB DF AC EF AD O DO EDF AD CAB DE AB DF AC 1 AB CD A= C= AEF= EFC= = A + B + C 180 + D 180 + + E N M D C B A 2 2 B=25 BCD=45 CDE=30 E=10 AB EF 3 1= 2= 3 FED=26 AGF=80 FH EFG PFH 1 AD BC ABC 15 DBC _. 2 1 A B 55 C ABC 2 C _ . 3 BD A
2、BCD M N AD AB MN BD DMC S BNC S . = 3 1 ABC A A 1 3 2 ABC D E F BC AD CE S ABC =8cm 2 AEF _cm 2 3 ABCD E F G H AB BC CD DA EG FH O AEOH BFOE CGOF 3 4 5 DHOG _. 1 l 1 AB l 2 1=50 2 _. 2 ABC A D 4 3 ABCD AD AD=4 BC=8 A B CD 1 3 A A= 1 3cm 5cm xcm x _. 2 2cm 9cm _. 3 ABC a b c 2 2 4 0 ab c . c _. 1 A B
3、 C D 2 ABC ACB C BD A ABC B ABC C ABC D ABC 3 5 3 25 A 3 B 4 5 C 6 7 D 8 5 1 P 2 3 90 75 15 90 54 36 A 30 B 29 C 10 D 9 1 ABC D BC S ABD =S ADC AD A B C D 2 ABC AD CE ABC AD=2 CE=4 AB BC= A 3 4 B 4 3 C 1 2 D 2 1 3 ABC CD BC AC=5cm DBC 25cm ADC 6 1 ABC A=20 CD BCA CDA DE CA EDA= CDB B 2 ABC E AC AEB=
4、 ABC 1 BAC AD CB BE D F EFD= ADC 2 ABC BAG AD CB BE D F 3 MON=40 OE MON A B C OM OE ON A B C O AC OE D OAC=x 1 AB ON ABO BAD= ABD x= BAD= BDA x= 2 AB OM x ADB x 7 1 A 90 B C 21 32 BDC=148 2 ABD ACD P A=50 D=10 P . 3 A=44 C=22 ADC ABC E. E . N O M C D B E A 8 1 ABC I I DE AI AB AC D E BIC BDI BAC 40 60 90 120 BIC BDI 2 XOY=90 A B OX OY BE ABY BE OAB C ACB A B 3 BP CP ABC B C 1 90 2 BPC A ABC ABCD BP CP B C BPC A D _
