Đáp án:
Giải thích các bước giải:
2cos(2x+π/4)+√3=0
⇔cos(2x+π/4)=-√3/2
⇔\(\left[ \begin{array}{l}2x+\pi/4=5\pi/6+k2\pi\\2x+\pi/4=-5\pi/6+k2\pi\end{array} \right.\)\(\left[ \begin{array}{l}x=7\pi/24+k\pi\\x=-13\pi/24+kN\end{array} \right.\) (k∈Z)
$\begin{array}{l}2\cos \left( {2x + \dfrac{\pi }{4}} \right) + \sqrt 3 = 0\\ \Leftrightarrow \cos \left( {2x + \dfrac{\pi }{4}} \right) = - \dfrac{{\sqrt 3 }}{2}\\ \Leftrightarrow \cos \left( {2x + \dfrac{\pi }{4}} \right) = \cos \dfrac{{5\pi }}{6}\\ \Leftrightarrow \left[ \begin{array}{l}2x + \dfrac{\pi }{4} = \dfrac{{5\pi }}{6} + k2\pi \\2x + \dfrac{\pi }{4} = - \dfrac{{5\pi }}{6} + k2\pi \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l}x = \dfrac{{7\pi }}{{24}} + k\pi \\x = \dfrac{{ - 13\pi }}{{24}} + k\pi \end{array} \right.\left( {k \in Z} \right)\end{array}$
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viết các biểu thức sau dưới dạng bình phương của 1 tổng x^2+2x=1 4x^2+12x+9
Calli : Muốn ở bên cậu mà khó NL : chơi thân vs nhau đc gần 8 năm mà h mỗi đứa 1 trường ko bik có thân đc như xưa hay ko =='
giúp em câu này với ạ, em làm hoài mà vẫn sai, chưa hỉu lí do sao lại sai nữa, giúp em với, 15. John smoked a lot a year ago, but now he doesn't smoke anymore. => John used___________________________________________________.
Exercise 1 - Fill in the blanks with the past simple or the past continuous: 1. When I ________________ (arrive) the teacher _________ (write) the summary. 2. He _____________________________ (cross) the road when I _________________ (see) him. 3. Why ____________________________ (they / shout) at you when I _______________ (wake up)? 4. They ________________________ (fix) the computer when I ______________ (open) the door. 5. __________________________ (Mary / break) her leg while she _______________________ (skate)? 6. I ________________________ (sleep) when she __________________ (knock) on the door. 7. When I _______________ (see) Jim at the disco he ________________________ (not / talk) to the DJ. 8. I ____________________________ (watch) a film on TV when the electricity ______________ (go) out. 9. The Titanic ________________________ (not / cross) the Pacific Ocean when it _______________ (strike) an iceberg. 10. Paul ____________________ (not / fall) while he _______________________ (run) away. 11. Carol ________________ (fall) asleep while she _________________________ (read) a book. 12. While my father _________________________ (drive) home, he _______________________ (not / answer) his mobile phone. 13. While I _________________________ (have) a driving lesson it ___________________ (start) to rain heavily. 14. When I ______________ (find) the wallet on the street I ___________ (go) to the police and I _______________ (turn) it in. 15. When Mrs Spencer ___________________ (walk) into the busy office, the secretary ___________________________ (talk) on the phone with a customer, several clerks _____________________________ (work) at their desks and two managers _______________________ (discuss) methods to improve customer service. 16. Last night, Sebastian _________________ (go) at Susan’s house about 9:00 pm, but she __________________ (not / be) there. She _______________________ (study) at a friend’s house. 17. Sam _________________________ (read) the newspaper while he ______________________ (wait) for the bus. 18. Yesterday I _______________ (see) Paul at the party and he ______________________ (not / dance) with Rachel.
Mn vẽ giúp em vs ạ, hứa 5 sao và ctrlhn ạ. Cảm ơn
Giúp em với em đang cần gắp lắm
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mình đang cần gấp lắm ạ,mong các bạn giúp mình cho 2 đường thẳng x'x và y'y cắt nhau tại O sao cho góc x'Oy' =1/2 góc xOy tính số đo của 4 góc tạo thành gọi Om là phân giác của góc xOy và Ox là phân giác của góc xOy' .chứng minh rằng om và on là 2 tia đối nhau tìm 3 cặp góc đối đỉnh trong hình
15. The children are looking forward to ………..on holiday. a. go b. going c. be going d. have gone 16. You must try not …….so many mistakes again. a. make b. making c. to make d. makes 17. He advised me …………….at this time. a. not to go out b. not go out c. not going out d. not to going ut 18. We always expect ……….as many good marks as possible. a. getting b. get c. to getting d. to get 19. This book is worthy ………for us. a. to read b. reading c. read d. be read 20. I have trouble ………late at nights a. work b. to work c. working d. works
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