第1个回答 2015-11-01
1.1
0112 3456789
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1.c2
./0 12 34 2.3 4 5
>?<@
61
D 62 15063 ∵S△AHC=14AC2,S△CFB=14BC2,S△A
BE=14
AB2
,∴S78=14AC2+14BC2+14AB2
=
14×2·AB2
=12AB2=92
.ABCD
6 9△ABC:,;<AB=10,BC=8,=>2<
AC<18,?BC>AC,=>2<AC<8,@ACAB',=>ACCDE4F6.+EFG
1.D 2.A 3.C 4.8 5.46.G:HCDI<x.9Rt△A
CD:,AD2=102-x2
;
9Rt△ABD:,AD2
=172
-(x+9)2.=>102
-x2
=172
-(x+9)2
,x=6.
=>A
D2
=64,AD=8.0212 34567HI
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J KLM NO>?<@
61 ∵Rt△ABE≌Rt△E
CD,∴∠AEB=∠E
DC.?∵∠EDC+∠DEC=90°,∴∠AEB+∠DEC=90°,∴∠AED=90°.
∵SPQABCD=SRt△ABE+SRt△DEC+SRt△AED,∴
12(a+b)(a+b)=12ab+12ab+12
c2
.RS,Ta2
+b2
=c2
.62
U!V.WI<3、4X2Y<Z[2\,12X./<25;@WI<4X2<12\,]^_`2X./<42
-32
=7.ABCD
BCXI<25F7.+EFG1.B 2.10
3.G:aAbAD⊥BCcdD,eA
D2=102-82=62
,∴AD=6(cm).
4.G:fghQijUklm,+Xn/QX2IA(a+b),opqXn/QX2I<c.+n/Qprs>tu<:(a+b)2,vs>tu<:12a
b×4+c2
.wxyz{tu/|,sT}(
a+b)2
=12
ab×4+c2.RSTc2=a2+b2.;~yhQvs>
34VS.
5.G:9Rt△ABC:,34VST,
AB=10cm,∴BE=AE=1
2AB
=
12
×10=5cm.HBD=x,TAD=BD=x,CD=8-x,9
Rt△ACD:,34VST,
CD2+AC2=AD2
,∴(8-x)2+62=x2,GTx
=254,∴BD=254
cm.0312 34567JK
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a2+b2=c2 b2=c2-a2 a2=c2-b本回答被网友采纳