2 1. > 2. 7 230 m 185 m
2. 1 ab ABCD BD x BCD x =a +b x>0 x="a +b a "a +a ="2ça ='2a 129
(1) 4cm5cm "4 +5 ='1ƒ6+25='4å1 (cm) (2) 4cm '2_4=4'2 (cm) 1 x (1) (2) 45 1 BC =CA =a ABC AB BC CA AB =BC +CA =a +a =2a AB = '2a AB >0 AB ='2a AB BC CA ='2aaa ='211 '211 2 xy (1) (2) 130
60 2 ABC A H AB BH HA AHBC BC =2BH BH =a AB =BC =2BH =2a ABH AH =AB -BH =(2a) -a =3a AH = '3a AH >0 AH ='3a AB BH HA =2aa'3a=21'3 21'3 3 xy (1) (2) 45 60 AB BC CA ='211 AB BC CA =21'3 131
4 AC AD p. 151 5 27.43 m 2 2 '2=1.414 3 6cm6cm8cm A BC H H BC BH =;2!; BC =;2!;_8=4(cm) ABH AH =øπab π-b H =" 6-4 ='2å0=2'5(cm) ABC ;2!;_BC _AH =;2!;_8_2'5=8'5(cm ) 8'5 cm 6 8cm 7 132
A B C B C 1 2 AC BC ABC AB AOB OB =3AB =2 2 OA =OB +AB =3 +2 =13 OA >0 OA ='1å3 4 A(24)B(-31) ABC C (21) BC =2-(-3)=5AC =4-1=3 AB =BC +AC =5 +3 =34 AB >0 AB ='3å4 '3å4 133
8 (1) A(21)B(15) (2) A(14)B(-31) (3) A(-24)B(0-1) (4) A(2-5)B(-4-2) 9 A(-25)B(2-1)C(51) ABC 500 m300 m AB A B A=B+CB=D+EC=F+G 134
2. 2 80 cm60 cm 200 cm 230 cm GEF EG AEG AG abc AG x AEG x =EG +c EFG EG =a +b x =a +b +c x>0 x="a +b +c 135
a "a +a +a ='3a (1) 3cm4cm5cm "3 +4 +5 ='5å0=5'2(cm) (2) 4cm '3_4=4'3(cm) p. 152 1 (1) 2cm3cm6cm (2) 5cm 1 r h V V=;3!;pr h 3cm 6cm h cm h +3 =6 h =6-3 =36-9=27 h>0 h=3'3(cm) V V=;3!;_(p_3 )_3'3=9'3p(cm ) 3'3 cm9'3p cm 2 6 cm 8cm (1) (2) 136
2 =;3!; 6cm 12 cm OABCD O H H ABCD AH =;2!;AC =;2!;_6'2=3'2(cm) OAH OHA=90 OH =OA -AH =12 -(3'2) =126 OH >0 OH =3'1å4(cm) V V=;3!;_(6_6)_3'1å4 V=36'1å4 (cm ) 3'1å4 cm36'1å4 cm 3 8cm (1) (2) (3) 100 cm 60 cm OABC ABC 137
V- 2 ab "a +b a '2a abc "a +b +c a '3a 1. (1) 3cm5cm (2) 5'2 cm 2. 10 cm 3. A(13)B(-25) 4. (1) 2cm4cm6cm (2) 2'3 cm 5. OABCD 6'2 cm 12 cm 138
V ABC C=90 a +b =c ABC a +b =c C=90 139