$\begin{array}{l} \left( {1 - \sin x} \right)\left( {2\sin x + 1} \right) = {\cos ^2}x\\ \Leftrightarrow \left( {1 - \sin x} \right)\left( {2\sin x + 1} \right) = 1 - {\sin ^2}x\\ \Leftrightarrow \left( {1 - \sin x} \right)\left( {2\sin x + 1} \right) = \left( {1 - \sin x} \right)\left( {1 + \sin x} \right)\\ \Leftrightarrow \left( {1 - \sin x} \right)\left( {2\sin x + 1 - 1 - \sin x} \right) = 0\\ \Leftrightarrow \left( {1 - \sin x} \right)\sin x = 0\\ \Leftrightarrow \left[ \begin{array}{l} \sin x = 0\\ \sin x = 1 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} x = k\pi \\ x = \dfrac{\pi }{2} + k2\pi \end{array} \right.\left( {k \in \mathbb{Z}} \right) \end{array}$
Đáp án:
x=kπ/2
Giải thích các bước giải:
(1-sin x)(2sin x+1)= cosx²
⇔2sin x+1-2sinx² -sinx= 1-sinx²
⇔1-sinx²-2 sinx -1+2sinx² +sin x=0
⇔sinx²-sinx=0
⇔sinx(sinx -1)=0
⇔sinx=0
hoặc sin x=1
⇔x=kπ hoặc x=π/2 +k2π
⇒x=kπ/2
II/ Choose the best answer:(2) 21. He is surprised __________that there are 54 ethnic groups in our country. A. to understand B. to study C. to know D. find 22. The Viet (or Kinh)have______number of people, account for about 86% of the population. A. large B. the large C. larger D. the largest 23. ________ ethnic group has a larger population, the Tay or the Ede? A. What B. Which C. Why D. Who 24.Ba spends his free time … volunteer work at a local orphanage. A. to do B. do C. to doing D. doing 25. He prefers ______A. go for a swim to study B. going for a swim to study C. going for a swim to studying D. go for a swim to studying 26. Martina has loved sports _____she was a child. A. since B. for C. when D. as 27. It has been the____ day in London for 35 years. A. hoter B. hotter C. hotest D. hottest 28. If you move to your left, you_____the church. A. will see B. are seeing C. has seen D. see 29. Is the rubbish______ every day? A. collect B. collecting C. collected D. be collected 30. Sooner or later a satellite _______ by a large piece of rubbish. A. will destroy B. will destroyed C. will be destroyed D. will been destroyed
Mọi người giúp em giải bài tập này với ạ!
làm hộ mik nhé mik vote 5 + ctlhn
để in văn bản, em sử dụng lệnh nào?
help me!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
II/ Choose the best answer:(1) 11. It is very dangerous …. in the polluted environment.A. to live B. lives C. living D. live 12. Our ………….. resources are limited so we should recycle all used things. A. nature B. natural C. naturing D. naturally 13. His car is the same color …. my uncle’s.A. alike B. as C. like D. to 14. This ruler ….. of plastic. A. make B. made C. is making D. is made 15. I take part ….. most youth activities of my school.A. in B. of C. on D. at 16. My mother enjoys_________ traditional food for our family, especially at Tet holiday. A. cook B. to cook C. cooking D. cookedss 17. My father sometimes goes _____ in the forests.He’d like to findsome more food for our family. A. hunt B. hunting C. to hunt D. hunted 18. Look! Some children are ____________the buffaloes. A. picking B. herding C. driving D. playing 19. The sky is _______here in the countryside because there are no buildings to block the view. A. tidy B. close C. dense D. vast 20.Is living in the city _________ than living in the country? A. more convenient B. as convenient C. most convenient D. so convenient
mn giúp mình vs mình cảm ơn xin lỗi vì đã lm phiền mn ạ Tìm từ 2 âm tiết có trọng âm khác. 11. A. below B. bathroom C. body D. city 12. A. country B. early C. husband D. cartoon 13. A. river B. paper C. lesson D. collect 14. A. sometimes B. locate C. student D. tired 15. A. under B. very C. behave D. yellow 16. A. bamboo B. winter C. weather D. after 17. A. improve B. study C. sugar D. summer 18. A. window B. table C. sorry D. repair 19. A. ready B. player C. person D. believe 20. A. become B. shopping C. travel D. website 21. A. bookcase B. finish C. away D. bedroom 22. A. across B. April C. jacket D. correct 23. A. orange B. apple C. monkey D. enough 24. A. Sunday B. winter C. example D. station 25. A. swimming B. idea C. writing D. woman 26. A. brother B. improve C. careful D. carpet 27. A. explain B. carrot C. daily D. modern 28. A. machine B. suppose C. complete D. extra 29. A. final B. enter C. subject D. return 30. A. crazy B. farmer C. receive D. ever
Cho 2 góc kề bù aoc và cob. Gọi om là tia phân giác của góc aoc. Kẻ tia on vuông góc với om(tia on nằm trong góc boc). Tia on là tia phân giác của góc nào. Vì sao
"Where is my umbrella?" she asked. -> She asked............................................................................................................................. "How are you?" Martin asked us. -> Martin asked us..................................................................................................................... He asked, "Do I have to do it?" -> She asked............................................................................................................................. "Where have you been?" the mother asked her daughter. → The mother asked her daughter..................................................................................................... "Which dress do you like best?" she asked her boyfriend. → She asked her boyfriend. ..................................................................................................... "What are they doing?" she asked. → She wanted to know..................................................................................................... "Are you going to the cinema?" he asked me. → He wanted to know..................................................................................................... The teacher asked, "Who speaks English?" → The teacher wanted to know..................................................................................................... "How do you know that?" she asked me. → She asked me..................................................................................................... "Has Caron talked to Kevin?" my friend asked me. → My friend asked me......................................................................................................
Kinh Dương Vương đóng đô ở đâu? ( Kinh Dương Vương ko phải vua Hùng đâu nha )
Loga.vn - Cộng Đồng Luyện Thi Trực Tuyến
