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a) Áp dụng định lý Pi-ta-go vào \(\Delta ABC\), ta có :
BC2= AB2+ AC2= 202+ 212= 400+ 441= 841(cm)
\(\Rightarrow\)BC= \(\sqrt{841}\)= 29(cm)
b) AD là phân giác Â
=> \(\dfrac{AB}{AC}\) = \(\dfrac{BD}{CD}\)
<=> \(\dfrac{AB}{BD}\) = \(\dfrac{AC}{CD}\) = \(\dfrac{AB+AC}{BD+CD}\) = \(\dfrac{41}{BC}\) = \(\dfrac{41}{29}\)
=> 29.AB = 41.BD
<=> BD = \(\dfrac{29.AB}{\text{41}}\) = \(\dfrac{29.20}{41}\)=\(\dfrac{580}{41}\)
DC= BC-BD= 29-\(\dfrac{580}{41}\)=\(\dfrac{609}{41}\)
1) ADME là h.b.h (vì có 2 cặp cạnh đối song song)
2) Vì ADME là hình chữ nhật nên O là trung điểm 2 đường chéo AM và DE.
Xét tam giác AHM vuông tại H, đường trung tuyến HO, khi đó HO = AO = OM
Vậy tam giác AHO cân ở O
3)
a, Tam giác ABC vuông tại A nên ˆDAE=900DAE^=900
Mà ADME là h.b.h nên tứ giác ADME là hình chữ nhật
b, Vì tứ giác AEMD là hình chữ nhật nên ED=AM
Để DE có độ dài nhỏ nhất thì AM có độ dài nhỏ nhất hay M là chân đường vuông góc hạ từ A xuống BC
Nếu bạn có thể giải xin hãy giải giúp mình nhé !
A . vi O la tam cua hinh vuong ABCD
=>AC cắt BD tại O
vi ABCD la hinh vuong(gt)
=> DB là đường phân giác của góc ADC
=> goc ADB = góc BDC=ADC/2 (1)
và BD là đường phân giác của ABC
=>góc ABD = góc DBC =ABC/2 (2)
Mà ADC=ABC(=90 do) (3)
tu (1), (2), (3)=>ADB=ABD
Ta co: OA vuong goc NM
Va OA vuong goc BD(ABCD la hinh vuong)
=>MN//BD
Ma ADB = ABD(CMT)
=>MNBD là hình thang cân
B. xet tu giac AEIF , co:
góc A = góc E = góc F=90 do
=> AEIF là hình chữ nhật
mà AI là đường phân giác của góc EAF
=> AEIF la hinh vuong
ai la nguoi yeu cua toi
Put the question tag on the end of these sentences.
1. You have heard about that,…
2. Nam did the work well,…
3. He didn’t have to speak to me,…
4. He won’t fall down,…
5. You wouldn’t the windown open,…
6. She used to beat his wife,…
7. She came very late,…
8. Come and see me tomorrow,…
9. That’s the sort of thing you would do,…
10. I’d better go,…
11. There is an examination tomorrow,…
12. She’s been studying English for two years,…
13. You can’t play tennis today,…
14. It is surely sunny today,…
15. Beverly will be attending the university in September,…
16. I’m never called “Scholar”,…
17. No one has come here,…
18. Everybody can learn how to swim,…
19. Hia family often have tea for breakfast,…
20. She never works on Sundays,…
21. You can speak English,…
22. He shouldn’t smoke,…
23. That job is hardly suitable for her,…
24. They were there,…
25. They arrived yesterday,…
26. She doesn’t want to go,…
27. He will come,…
28. Your father is a teacher, ….
29. There are more countries north of the equator than south of it,…
30. You have never been in Italy,…
31. You have a ket to the game,…
32. You don’t know of any vacant apartments, …
33. He doesn’t need a furnished apartment,…
34. But I guess he can always rent some,…
35. The movers aren’t packing the books for us,…
36. You have lived in Hollyood for many years,…
37. You didn’t know anyone here at first,…
38. Sally turn in her report,…
39. That’s Bob’s,…
40. No one died in the accident,…
41. You’re working on another screenplay now,…
42. Speaking of kids, you have some of your own, …
43. That depends on what you mean by a long time,…
44. We should call Rita,…
45. I’m supposed to be here,…
46. Nothing wrong,…
47. You are still wanted by the police,…
48. We went to Stan’s holiday party last year,…
49. Tom and Fred hadn’t been to Florida before then,…
50. I’m asually right about the weather,…
51. Nobody called on the phone,…
52. Everything are OK,…
53. Everyone took the test,…
54. There are a lot of people here,…
55. They had to go home,…
56. The little children were let go away,…
57. Mary realy goes out on Sundays,…
58. There is something wrong with the new car,…
59. That is true story,…
60. The qualiyof these recordings is not very good,…
61. Let’s go to the cinema tonight,…
62. This book isn’t very interesting,…
63. Tom has never written to you,…
64. Mr. Brown needs to leave right now,…
65. Everything is all right now,…
66. Listen to what I am staying,…
67. Fruit juices and milk are healthyful drinks,…
68. Tom had great difficulty finding a jobs,…
69. The police come to the side of the accident,…
70. Ba complained about the noise,…