cứu em với mn :(

Cho đường tròn (O;R), kẻ đường kính BC, lấy 1 điểm A trên (O)  sao cho AB = R.
a) Chứng minh tam giác ABC vuông. Tính độ dài AC theo R.
b) Trên tia OA lấy D sao cho A là trung điểm của OD. Chứng minh DB là tiếp tuyến của (O).
c) Vẽ tiếp tuyến DM với (O) (M là tiếp điểm). Chứng minh tam giác BDM đều.
mn giúp em với ạ, em cần gấp!

Bài 7. Cho (O;5cm) đường kính BC, lấy điểm A thuộc (O) sao cho AB = 6cm. Tiếp tuyến tại B của (O) cắt
tia CA tại D.
a) Chứng minh tam giác ABC vuông và tính AC.
b) Qua O kẻ đường vuông góc với AB cắt BD tại M. Chứng minh MA là tiếp tuyến của (O)c) Gọi K là giao điểm của MC và (O). Chứng minh đường thẳng BK chứa tia phân giác của góc AKD

mn có thể cho em xin các điều kiện cm tiếp tuyến và cách nhớ nếu được không ạ!

Exercise 2: Viết lại câu sao cho nghĩa không đổi.

1. The last time Ms.Mai came back to her hometown was 4 years ago.

=> She hasn't............................................................................................................

2. They started working as a bank manager a month ago.

=> He has.................................................................................................................

3. It has been 2 years since he first flew to Malaysia.

=> He have................................................................................................................

4. I last had my hair cut in December.

=> I haven't................................................................................................................

5. The last time we talked to each other was a month ago.

=> We haven't.............................................................................................................

6. It is a long time since the friends last met.

=> The friends haven't...................................................................................................

7. When did you have it?

=> How long...........................................................................................................?

8. This is the first time I had such a delicious meal.

=> I have never.............................................................................................................

9. I haven't seen my friends for 15 days.

=> The last................................................................................................................

10. Today is Saturday. I haven't taken a bath since Wednesday.

=> It is........................................................................................................................

VII. Read the following letter. Decide if the statements are True or False, and choose the correct answers (A, B, C or D) for the question 5     (1.5 pts)

The first jeans were made in Genoa,Italy.The first people to wear jeans were sailors in the 16th century.

In 1950, popular movie and music stars like Elvis Presley and James Dean started wearing jeans.  Jeans became so popular because they meant freedom. 

In 1960 they started to decorate their jeans with flowers and colorful designs or to tear and rip the jeans.

But in 1980 jeans became very expensive. Famous fashion designers like Calvin Klein began making designer jeans. Young people wanted to wear certain brands to show their style. There was a lot of pressure to keep up with the trend. Everybody wanted to be fashionable. Jeans were considered the uniform of youth.

1.      The first people wearing jeans were sailors in the1600s.

2.      Jeans symbolized freedom.

3.      In 1980 jeans became very inexpensive.

4.      Jeans were considered the school uniform.

5.      What are decorated on jeans in 1960?

A. flowers        B. colorful designs         C. flowers and colorful designs      D. designs

In the 1980s jeans finally became high (1)__________ clothing, when famous designers started (2)________________their own styles of jeans, with their own labels (3)______________ them. Sales of jeans went up and up. But in the 1990s the (4)___________economic situation got worse, and the sale of jeans (5)__________growing. However, jeans have never been out of fashion, and today- young ( 6 ) ______________is still fond of wearing them.
 

1.Tricia won’t join us for the trip.

àWe wish _________________________________________________________

2.I don’t have money to go abroad.

àI wish____________________________________________________________

3.It’s a pity I don’t know where he is.

àI wish____________________________________________________________

4. We can’t go out because of heavy rain.

àWe wish__________________________________________________________

5. Linh didn’t see “ Titanic” long ago.

à Linh has _________________________________________________________

6. John smoked a lot a year ago, but now he doesn’t smoke any more.

àJohn used_________________________________________________________

7. Mary usually stays at home on Sundays.

àMary is used_______________________________________________________

8. Tom no longer gets up late in the morning.

àTom used _________________________________________________________

9. Please keep silent in the classroom.

àI’d rather you______________________________________________________

10.The last time she went out with him was nearly months ago.

àIt is______________________________________________________________