`~rai~`
\(1.\dfrac{1-\cos x}{\sin x}=\dfrac{\sin x}{1+\cos x}\\\text{Giả sử,ta có:}\\\dfrac{1-\cos x}{\sin x}=\dfrac{\sin x}{1+\cos x}\\\Leftrightarrow (1-\cos x)(1+\cos x)=\sin^2x\\\Leftrightarrow 1-\cos^2x=\sin^2x\\\Leftrightarrow \sin^2x=\sin^2x.\text{(luôn đúng)}\\\Rightarrow\text{Điều giả sử là đúng}\\\Rightarrow\dfrac{1-\cos x}{\sin x}=\dfrac{\sin x}{1+\cos x}.(đpcm)\\2.\left(1-\dfrac{1}{\cos x}\right)\left(1+\dfrac{1}{\cos x}\right)+\tan^2x=0\\\text{Xét VT=}\left(1-\dfrac{1}{\cos x}\right)\left(1+\dfrac{1}{\cos x}\right)+\tan^2x\\\quad\quad\quad=1-\dfrac{1}{\cos^2x}+\tan^2x\\\quad\quad\quad=1-(1+\tan^2x)+\tan^2x\\\quad\quad\quad=1-1-\tan^2x+\tan^2x\\\quad\quad\quad=0.\\\Rightarrow \left(1-\dfrac{1}{\cos x}\right)\left(1+\dfrac{1}{\cos x}\right)+\tan^2x=0.(đpcm)\)
1.
`\frac{1-cosx}{sinx}=sinx/(1+cosx)`
`=>(1-cosx)(1+cosx)=sin^2x`
`<=>1-cos^2x=sin^2x`
`<=>sin^2x+cos^2x=1` (luôn đúng)
Vậy `\frac{1-cosx}{sinx}=sinx/(1+cosx)` $\text{(đpcm)}$
2.
`(1-1/cosx)(1+1/cosx)+tan^2x=0`
`VT=(1-1/cosx)(1+1/cosx)+tan^2x`
`=1-1/cos^2x+tan^2x`
`=1-(1+tan^2x)+tan^2x`
`=0=VP`
Vậy`(1-1/cosx)(1+1/cosx)+tan^2x=0` $\text{(đpcm)}$
phản ánh sự đối lập hoàn toàn giữa ............ với tình cảnh đang bị................
cali : Sắp đến sinh nhật Khánh rồi đấy , Khánh nhắc nhẹ vậy thôi ! Tone màu đỏ và đen Trang trí vài cái liên quan đến sinh nhật nha
làm giúp em câu 5 6 phần 1 với ạ em cảm ơn
Hi Oliver. How are you? B: I’m fine thanks. I’m just (1) ......(do) my homework. I (2).....(think) it’s really hard. And you? A: I’m (3).......(go) to singing class. I normally (4)......(have) it on a Tuesday night. B: But did you (5) ......(do) your homework? It’s for tomorrow morning! A: I (6)......(do) it in class, while the teacher wasn’t (7)..... (look). B: You shouldn’t (8)......(spend) your time in class doing homework! A: I know, but I don’t (9)..... (have) any spare time. I’m (10)......(practise) for a big singing competition and want to spend my time on that.
Circle the letter A, B, C, or D to indicate the correct answer to each of the following questions. We should wait for the traffic lights…………… before we cross the street. A. turn yellow B. to turn green C. to turn yellow D. turn green 10 Circle the letter A, B, C, or D to indicate the correct answer to each of the following questions. I haven"t got ................. bread left for breakfast. A. any B. an C. a D. some
Choose the best answer to indicate the correct answer to each of the following questions: "Robots can’t play sports because they can’t ______ over ." * stand bend act teach
Sắp xếp theo thứ tự sao cho đúng về vai trò của Quang Trung trong sự nghiệp đấu tranh chống ngoại xâm, nội phản. 1. Có công lao to lớn trong việc tiêu diệt quân xâm lược Xiêm. 2. Có công lao to lớn trong việc đem quân ra Bắc lật đổ chúa Trịnh, tôn phò vua Lê đánh bại quân xâm lược Thanh. 3. Có công to lớn trong việc đập tan chúa Nguyễn ở Đàng Trong. 4. Cùng Nguyễn Nhạc, Nguyễn Huệ, Nguyễn Lữ dựng cờ khởi nghĩa.
III, Read the passage, then answer the questions below (2pts) Living in the country is something that people from the city often dream about. However, in reality, it has both advantages and disadvantages.There are certainly many advantages to living in the country. First, you can enjoy peace and quietness. Moreover, people tend to be friendlier. A further advantage is that there is less traffic, so it is safer for young children. However, there are certain disadvantages or drawbacks to life outside the city. First, because there are fewer people, you are likely to have few friends. In addition , entertainment is difficult to find, particularly in the evening. Furthermore, the fact that there are fewer shops and services means that it is hard to find jobs. In short, it can be seen that the country is more suitable for some people than others. On the whole, it is often the best for those who are retired or who have young children. In contrast, young people who have a career are better provided in the city. Questions: 1, Does living in the country have only good points ? ………………………………………………………………………………………… 2, How many advantages does living in the country have ? ………………………………………………………………………………………… 3, Is it safer or more dangerous for young chidren to live in the country ? …………………………………………………………………………………………. 4,Why is it hard for you to find jobs in the country ? ………………………………………………………………………………………...... 5,Who is living in the country the best for ? …………………………………………………………………………….......................
A.unreussable B.unpolluted C.unhappy D.polluted
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