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a, áp dụng Pytago cho tam giác ABC ta đc: BC=
diện tích tam giác ABC=1/2. AB.BC = 1/2 AH.BC => AB.BC=AH.BC=> AH=15.8:17=120/17
b, Tứ giác AMNH là hình chữ nhật vì có 3 góc vuông.
suy ra MN=AH = 120/17
c, Ta thấy tam giác AMH đồng dạng tam giác AHB (g.g) suy ra AM/AH = AH/ AB => AM.AB =AH^2
tam giác ANH đồng dạng tam giác AHC (g.g) => AN/AH = AH/AC => AN.AC = AH^2
suy ra AM.AB = AN.AC.
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
III
1) Should Jahn be helped with the sewing ?
2) Judy's car is being repeared by the mechanic .
3) Must the test be finished before ten ?
4) A computer is used to that job nowadays .
5) All travel expenses for this training course must be paid by employers .
6) Were they taken in by her story .
7) I was kept waiting for half an hour by the bank manager .
8) Has this word been spelt wrongly .
9) He will be seen off at the airport by all his friends ,
10) Beer used to be druck for breakfast in England years ago .
- I was kept waiting for half an hour by the bank manager.
- Has this word been spelt wrongly?
- He will be seen off at the airport by all his friends.
- Beer used to be drunk for breakfast in England years ago.
- The letter might have been sent to the wrong address.
- The floor was being cleaned when I arrived.
- The hole is being digged on the wrong side of the road.
- Your money is going to be stolen if you're not careful.
- Have you ever been asked for your opinion?
- I am not impressed by Alan's knowledge of art.
- How are candles made?
- Tea can't be made with cold water.
- When is the results of the contest going to be announced?
- The police wasn't informed that there had been a mistake.
- Where will you be sent by your company next year?
- The children were looked after by whom when you were away?
- Look! The seals are being fed.
- The book had been returned to the library by Kathy.
- By this time tomorrow, the announcement will have been made by the president.
- People's breathing was being affected by the pollution in the city.
-Those papers haven't been signed by Mrs.Andrew yet. Have they been signed by Mr.Andrew yet?
- Is that airplane being flown by a student pilot?
- Where was the 1988 Olympic Games held?
-Are those tractors made in this country, or are they imported?
1.Should Jane be helped with the sewing?
2.Judy's car is being repaired by the mechanic.
3.Must the test be finished before ten?
4.A computer is used to do that job nowadays.
5.All travel expenses for this training course must be paid by employers.
6.Were they taken in by her story?
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