.在Rt△ABC中,∠BAC=90°,在BC上取一点D ,使BD=AB,E为BC的中点,且EF‖AD,交AB于F.求证:DF=BC/2
2.已知:AD是Rt△ABC斜边BC上的高,∠B的平分线交AD于M,交AC于E,∠DAC的平分线交CD于N.求证:四边形AMNE为菱形.
3.在梯形ABCD中,AD‖BC,∠ABC的平分线BE交CD于E,且E 是DC的中点.求证:CD=AD+BC
4.在Rt△ABC中,∠BAC=90°,AD⊥BC,垂足为D,BE平分∠ABC交AD于E ,EF‖BC交AC于F.求证:AE=CF
5.△PCD, 在PC上任取一点E,连接ED;在PD上任取一点F,连接CF;分别过点E.F作BE‖CF,AF‖DE,连接AB.求证:AB‖CD
6.已知一个等边三角形,其内部一点到各个顶点的距离分别是3 4 5,请问三角形的边长是多少?
7..(本题满分6分)如图,DB‖AC,且DB= AC,E是AC的中点,求证:BC=DE.
8.如图,在正方形ABCD中,点E、F分别在CD、BC上,且BF=CE,连结BE、AF相交于点G,则下列结论正确的是 ( )
(A)BE=AF (B)∠DAF=∠BEC
(C)∠AFB+∠BEC=90° (D)AG⊥BE
9.、(02年湖北黄冈)已知:如图1,AB⊥BD,CD⊥BD,垂足分别为B、D,AD和BC相交于点E,EF⊥BD,垂足为F,我们可以证明 成立(不要求考生证明).
若将图1中的垂线改为斜交,如图2,AB‖CD,AD,BC相交于点E,
过点E作EF‖AB,交BD于点F,则:
(1) 还成立吗?如果成立,请给出证明;如果不成立,请说明理由;
(2) 请找出S△ABD,S△BED和S△BDC间的关系式,并给出证明.
10.:做HC⊥AC于C,延长AE交HC于H.
在△BAM中,∠BAM=90°,AE⊥BM => ∠ABM=∠MAE
AB=AC,∠HCA=BAM
=>△ABM≌△CAH
=>HC=AM=MC(M为AC的中点),∠FCM=∠HCF=45°,FC=FC
=>△CHF≌△CMF
=>∠CMF=∠AHC
∠AHC=∠AMB
=>∠AMB=∠CMF
3X+18=52 x=34/3
4Y+11=22 y=11/4
3X*9=5 x=5/27
8Z/6=48 z=36
3X+7=59 x=52/3
4Y-69=81 y=75/4
8X*6=5 x=5/48
7Z/9=4 y=63/7
15X+8-5X=54 x=4.6
5Y*5=27 y=27/40
8x+2=10 x=1
x*8=88 x=11
y-90=1 y=91
2x-98=2 x=50
6x*6=12 x=1/3
5-6=5x x=-1/5
6*x=42 x=7
55-y=33 y=22
11*3x=60 x=20/11
8-y=2 y=-6
1.x+2=3
2.x+32=33
3.x+6=18
4.4+x=47
5.19-x=8
6.98-x=13
7.66-x=10
8.5x=10
9.3x=27
10.7x=7
11.8x=8
12.9x=9
13.10x=100
14.66x=660
15.7x=49
16.2x=4
17.3x=9
18.4x=16
19.5x=25
20.6x=36
21.8x=64
22.9x=81
23.10x=100
24.11x=121
25.12x=144
26.13x=169
27.14x=196
28.15x=225
29.16x=256
30.17x=289
31.18x=324
32.19x=361
33.20x=400
31.21x=441
32.22x=484
33.111x=12321
34.1111x=1234321
35.11111x=123454321
36.111111x=12345654321
37.46/x=23
38.64/x=8
39.99/x=11
40.1235467564x=0
41.2x+1= -2+x
42.4x-3(20-x)=3
43..-2(x-1)=4
44.3X+189=521
45.4Y+119=22 5
46.3X+77=59
47.4Y-6985=81
48.X=0.1
49.5X=55.5
50.Y=50-85
(-8)-(-1) =-7
45+(-30) =15
-1.5-(-11.5) =10
-0.25-(-0.5) =0.25
15-【1-(-20-4)】 =-10
-40-28-(-19)+(-24) =-73
22.54+(-4.4)+(-12.54)+4.4 =10
(2/3{三分只二 “/”是分数线}-1/2)-(1/3-5/6)=2/3
2.4-(-3/5)+(-3.1)+4/5 =0.7
(-6/13)+(-7/13)-(-2) =1
3/4-(-11/6)+(-7/3) =1/4
11+(-22)-3×(-11) =22
(-0.1)÷0.5×(-100) =20
(-2)的3次方-9 =-17
23÷[-9-(-4)] =-23/5
(3/4-7/8)÷(-7/8) =1/7
(-60)×(3/4+5/6)=-95
[-|98|+76+(-87)]*23[56+(-75)-(7)]-(8+4+3)
68/21-8-11*8+61
-2/9-7/9-56
4.6-(-3/4+1.6-4-3/4)
1/2+3+5/6-7/12
[2/3-4-1/4*(-0.4)]/1/3+2
22+(-4)+(-2)+4*3
-2*8-8*1/2+8/1/8
(2/3+1/2)/(-1/12)*(-12)
(-28)/(-6+4)+(-1)
2/(-2)+0/7-(-8)*(-2)
18-6/(-3)*(-2)
(5+3/8*8/30/(-2)-3
(-84)/2*(-3)/(-6)
-1+2-3+4-5+6-7
-50-28+(-24)-(-22)
-19.8-(-20.3)-(+20.2)-10.8
0.25- +(-1 )-(+3 )
-1-〔1-(1-0.6÷3)〕×〔2-(-3)×(-4)〕
0÷(-4)-42-(-8)÷(-1)3
-32-(-3) 2-(-3)3+(-1)6
3×(-2)2+(-2×3)2+(-2+3)2
(-12)÷4×(-6)÷2
(-12)÷4×(-6)×2
75÷〔138÷(100-54)〕
80400-(4300+870÷15)
1437×27+27×563
〔75-(12+18)〕÷15
2160÷〔(83-79)×18〕
280+840÷24×5
325÷13×(266-250)
85×(95-1440÷24)
58870÷(105+20×2)
1437×27+27×563
81432÷(13×52+78)
[37.85-(7.85+6.4)] ×30
156×[(17.7-7.2)÷3]
(947-599)+76×64
36×(913-276÷23)
-(3.4 1.25×2.4)
(31.8 3.2×4)÷5
194-64.8÷1.8×0.9 36.72÷4.25×9.9
3.416÷(0.016×35)
0.8×[(10-6.76)÷1.2]
(136+64)×(65-345÷23)
(6.8-6.8×0.55)÷8.5
0.12× 4.8÷0.12×4.8
(58+37)÷(64-9×5)
812-700÷(9+31×11)
120-36×4÷18+35
(284+16)×(512-8208÷18)
9.72×1.6-18.305÷7
4/7÷[1/3×(3/5-3/10)]
(4/5+1/4)÷7/3+7/10
12.78-0÷( 13.4+156.6 )
37.812-700÷(9+31×11)
(136+64)×(65-345÷23)
3.2×(1.5+2.5)÷1.6
85+14×(14+208÷26)
(58+37)÷(64-9×5)
(6.8-6.8×0.55)÷8.5
(284+16)×(512-8208÷18)
0.12× 4.8÷0.12×4.8
(3.2×1.5+2.5)÷1.6
120-36×4÷18+35
10.15-10.75×0.4-5.7
5.8×(3.87-0.13)
+4.2×3.74 347+45×2-4160÷52
32.52-(6+9.728÷3.2)×2.5 87(58+37)÷(64-9×5)
[(7.1-5.6)×0.9-1.15] ÷2.5 (3.2×1.5+2.5)÷1.6
5.4÷[2.6×(3.7-2.9)+0.62] 12×6÷(12-7.2)-6
3.2×6+(1.5+2.5)÷1.6 (3.2×1.5+2.5)÷1.6
5.8×(3.87-0.13)+4.2×3.74
33.02-(148.4-90.85)÷2.5