A= cos 20° + cos 40° + cos 140° + cos 160° + cos 180°

= (cos 20° + cos 160°) + (cos 40° + cos 140° ) + cos 180°
= (cos 20° - cos 20°) + (cos 40° - cos 40°) - 1
= -1
Mấy dạng này (cùng cos hoặc cùng sin) nhóm cặp 2 số có góc cộng lại bằng 180° là làm được.

là một nhóm sinh vật tiêu thụ hoặc hấpthụ cacbon hữu cơ (thay vì cố định cacbon từ các nguồn vô cơ như cacbon dioxit) để có thể sản xuất năng lượng và tổng hợp các hợp chất để duy trì sự sống.
Nguồn: Wikipedia

Vì trên da nó có tế bào nha.

Các giọt coaxecva được hình thành từ hỗn hợp 2 dung dịch keo khác nhau đông tụ lại thành những giọt rất nhỏ.

Sán lông thích nghi với đời sống bơi lội tự do.

Theo t thì có 2 cách sau:

=> Because Sue is no longer interested in that dress, she won't buy that.
=> Sue will not buy that dress despite/ in spite of the fact that she is no longer interested.

1.he gave up smoking

=> he used to smoke.

2.it was thought that the woman had been killed

=> the woman was thought to had been killed.

3. i wish i were rich

=>if wish i were rich.

4.i find it uninteresting to do this work

=> i am fed up with doing this work ( be fed up with: chán)

5.i used to go fishing with my father

=> i don't go fishing with my father anymore.

6 i remember my father took me to the city

=> i remembered i am used to being taken to the city by my father.

7.i didn`t arrive in time to see them off

=> i wasn't early enough to see them off.

Popular/ tourist/ sights/ include/ famous/ Harbour Bridge/ and Sydney Opera House/.

=> The popular tourist of sights include famous Harbour Bridge and Sydney Opera House.

BT dạng viết lại câu cho nghĩa không đổi:
1. This last time she came back to her hometown was 4 years ago.

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

2. He started working as a bank clerk 3 months ago.

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

3. It has been 5 years since we first flew to Singapore.

=> We have....................................................................................

4. I last had my hair cut in November.

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

5. The last time we called each other was 5 months ago.

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

6. It is a long time since we last met.

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

7. When did you have it?

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

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

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

9. I haven't seen him for 8 days.

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

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

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