Giải thích các bước giải:
ta có $S_{ABC}= \frac{a^2\sqrt3}{4}$
ta có :
$\widehat{[(ACC'A');(ABC)]}=\widehat{[AC';AC]}=\widehat{CAC'}=30^o$
áp dụng công thức lượng giác trong ΔACC' ta có;
⇒$tan30^o=\frac{CC'}{a}⇒CC'=\frac{a\sqrt3}{3}$
⇒$V_{ABCA'B'C'}=\frac{a\sqrt3}{3} \frac{a^2\sqrt3}{4}=\frac{a^3}{4}$
Vậy đáp án $\frac{a^3}{4}$
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Đọc đoạn trích sau và hoàn thành các yêu cầu bên dưới: Anh đội viên nhìn Bác Càng nhìn lại càng thương Người Cha mái tóc bạc Đốt lửa cho anh nằm. a. Đoạn trích trên được trích trong văn bản nào? Tác giả là ai? Phương thức biểu đạt nào? b. Hình ảnh nào trong khổ thơ gây ấn tượng trong em? c. Nêu nội dung chính của khổ thơ. d. Tìm câu thơ có sử dụng phép tu từ ẩn dụ.
I. Put the verbs between brackets in their correct Infinitive or Gerund form : 1. The children are busy (collecting ) shells on the beach. 2. She had to ask the boys (to stop) (making) noise. 3. Our teacher has promised (to help) us (preparing) for the exam. 4. I’d love (having) an opportunity of (to meet) you again. 5. He enjoys (listening) to his own voice. 6. Is (boiling) or (fry) the best way of (cooking) this fish? 7. It’s no use your (asking) him (to lend) you any money. 8. She stopped (talking) as if waiting for him (to speak). 9. My uncle used to (show) me where (to go) and what (to buy). 10. He suggested (start) a new business. 11. We had better (visit) her in hospital. 12. It's very easy to do, so stop (worry)! 13. Could you please stop (making) so much noise? 14. The phone rang while Ann was having dinner. She didn't answer it. She just carried on (eat). 15. The thief got into the house because I forgot (close) the window. 16. I've arranged (play) tennis tomorrow afternoon. 17. One day I'd like to learn (fly) an aero plane. 18. Why do you keep on (look) at me like that? 19. I don't enjoy (write) letters. 20. Why hasn't Sue arrived yet? She promised not (be) late. 21. Jill has decided not (buy) a car. 22. I can't help (wonder) why he did that. 23. He advised us (book) our tickets in advance. 24. Do you remember (dance) on the beach? 25. I look forward to (hear) from you. 26. They allowed us ( play) in the garden. 27. She reminded me (post) the letter. 28. I am sorry (inform) you that you haven't passed the exam. 29. You had better (explain) the rules to her. 30. I can't get used to (live) alone.
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mn giúp mk với ạ 2 câu số hoi ai đc 1 câu cũg đc ạ
1 we hope that the test tomorrow (not be)difficult
chứng minh n mũ 2 chia 5 dư 0,1,4
Kể lại một kỉ niệm đáng nhớ ghi vở
làm đúng hứa vote 5 sao III. Read the following passage, then choose a word from the box and write the correct word next to numbers 1-5. There is one exemple. roofs non - polluting are renewable the sun Solar energy is a long lasting source (0)..of.. energy, and it can be used almost anywhere. To generate solar energy, we only need solar cells and (1).....................! Solar cells can easily be installed on house (2) ................., so we don’t need any new space. Compared to other (3)...................... sources, they also possess many advantages: wind and water power rely on turbines which (4).................noisy, expensive and which take up large space. Solar cells are totally silent and (5).......................... As they have no moving parts, they require little maintenance and have a long lifetime.
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