K
Khách

Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.

Vd7:

b) Ta có: \(\sin^2\widehat{A}+\cos^2\widehat{A}=1\)

\(\Leftrightarrow\sin^2\widehat{A}=1-\dfrac{25}{169}=\dfrac{144}{169}\)

hay \(\sin\widehat{A}=\dfrac{12}{13}\)

\(\Leftrightarrow\cot\widehat{A}=\dfrac{5}{13}:\dfrac{12}{13}=\dfrac{5}{12}\)

\(\Leftrightarrow\tan\widehat{B}=\dfrac{5}{12}\)

4 tháng 8 2021

vd5 :cos67o,sin30o,sin38o,cos42o ,sin75o

        tan25o,  tan27o, cot50o,cot49o,tan80o

 

8 tháng 3 2022

\(\dfrac{-1}{12},\dfrac{-3}{4},\dfrac{2}{9},\dfrac{7}{6}\)

8 tháng 3 2022

\(-\dfrac{1}{12},-\dfrac{3}{4},\dfrac{2}{9},\dfrac{7}{6}\)

21 tháng 2 2023

MSC : `24`

`-5/6=-5.4/6.4=-20/24`

`7/8=7.3/8.3=21/24`

`7/24=7/24`

`-3/4=-3.6/4.6=-18/24`

`2/3=2.8/3.8=16/24`

`1=24/24`

Sắp xếp các phân số sau theo thứ tự tăng dần : 

`-20/24;-18/24;7/24;16/24;21/24;24/24`

có ai biết làm bài này không giúp mình với mình đang cần rất rất là gấp mong các bạn giúp cho , xin cảm ơnII. Choose the best answer1.I come from Canada. Where .................you..................from?a. do.............come         b. did ...... come     c. are ..........coming        d, have .....come2. The telephones…………..by Alexander Graham BellA. is invented                 B. is inventing                C. Invented           D. was invented3. The swimming pool...
Đọc tiếp

có ai biết làm bài này không giúp mình với mình đang cần rất rất là gấp mong các bạn giúp cho , xin cảm ơn

II. Choose the best answer

1.I come from Canada. Where .................you..................from?

a. do.............come         b. did ...... come     c. are ..........coming        d, have .....come

2. The telephones…………..by Alexander Graham Bell

A. is invented                 B. is inventing                C. Invented           D. was invented

3. The swimming pool .............. at 9 o’clock and ............ at 18.30 everyday.

a. opens............. closes   b. opens ...... closed      c. opened...... closed    d. opened......... closes

4. Three swimmers, Paul, Ed, and Jim, ................ now in competition  for medals.

a. is                       b. has been                      c. had been            d. are

5. Listen ! I .............. somebody knocking at the front door. 

a. am hearing         b. heard                          c. have heard         d. hear

6.. ………………………………………..yet?

A. Have the letters been typed            B. Have been the letters typed

C. Have the letters typed                    D. Had the letters typed

7. At 5 o’clock yesterday evening, I ……………my clothes.

a. am ironing         b. have ironed       c. ironed               d. was ironing.

8. I ………………..along the street when I suddenly heard footsteps behind me.

a. was walking      b. am walking        c. walk                            d. walked.

9. She ………….German for two years.

a. has learnt           b. is learning         c. learn        d. learns.

10. When  I last………..Jane, she ………..to find a job.

a. see/was trying    b. saw/was trying c. have seen/tried            d. saw/tried.

12. French is a…………language to learn than English is.

        A. difficult      B. more difficult       C. most difficult        D. more and more difficult

13. The more polluted air we breathe,…….we get.

          A. the more weaker                  B. the more weak

          C. the weaker                           D. weaker more

14. The more we study, the……we are.

          A. more good                 B. better               C. better than        D. good

15. The more I tried my best to help her, ……….she became.

          A. less lazy                     B. the lazier           C. the more lazy    D. lazier

16. The weather becomes………………

          A. colder with colder                                   B. colder and colder

          C. colder and more colder                            D. more and more cold

17. The more he slept,…………….irritable he became.

          A. the most                     B. the vey more     C. much more       D. the more

18. ………..he worked, the more he earned.

          A. The more hard           B. The hard           C. The harder        D. The hardest

19. ………I get to know Jim, the more I like him.

          A. For more                    B. More                C. The more D. The most

20. The competition makes the price of goods……….

          A. most cheap and cheap                    B. cheaper and cheaper

          C. more cheap and more cheap           D. cheaper and more cheaper

III. Rewrite:
1) Although Tom was a poor student, he studied very well.
=> In spite of ………………………………………………………
2) Mary could not go to school because she was sick.
 Because of ………………………………………………………………..
3) Although the weather was bad, she went to school on time.
=> Despite ……………………………………………………………..
4) My mother told me to go to school although my stomachache was sick.
=> In spite of ………………………………………………………………..
5) Because there was a big storm, I stayed at home.
=> Because of ……………………………………………………..
6) Tom was admitted to the university although his grades were bad.
 Despite …………………………………………………………………………
7) Although she has a physical handicap, she has become a successful woman.
=> Despite ……………………………………………………………………….
8) In spite of his good salary, Tom gave up his job.
=> Although………………………………………………………..

1
18 tháng 8 2021

II.

1. a

2. d

3. a

4. d

5. d

6. a

7. d

8. a

9. a

10. b

12. b
13. c

14. b

15. b

16. b

17. d

18. c

19. c

20. b

III.

1. In spite of being a poor student, Tom studied very well.

2. Because of her sickness, Mary could not go to school.

3. Despite the bad weather, she went to school on time.

4. In spite of my sick stomachache, my mother told me to go to school.

5. Because of the big storm, I stayed at home.

6. Despite his bad grades, Tom was admitted to the university.

7. Despite her physical handicap, she has become a successful woman.

8. Although his salary was good, Tom gave up his job.

18 tháng 8 2021

cảm ơn bạn nhiều ạ!!

4 tháng 4 2017

Tăng dần:8/-15;-19/30;34/45;17/20.

4 tháng 4 2017

Dùng phương pháp quy đồng nha.

17/20= 153/180

-19/30= -114/180

34/45= 136/180

8/-15= -96/ 180

Vì: -114< -96< 136< 153

=> -114/180 <-96/ 180 < 136/180 < 153/180

=> -19/30< -8/15< 34/ 45< 17/20

6 tháng 8 2021

Bài 1 : 
$Ca + 2H_2O \to Ca(OH)_2 + H_2$

Khí ẩm $H_2$ được làm khô bằng canxi vì $H_2$ không phản ứng với $Ca(OH)_2$

Khí ẩm $CO_2,SO_2$ không thể làm khô bằng canxi vì chúng phản ứng tạo sản phẩm khác

Bài 2 : 

2 tấn = 2000 kg

$m_{CaCO_3} = 2000.80\% = 1600(kg)$
$CaCO_3 \xrightarrow{t^o} CaO + CO_2$
$n_{CaO} = n_{CaCO_3\ pư} = \dfrac{1600}{100}.90\% = 14,4(kmol)$
$m_{CaO} = 14,4.56 = 806,4(kg)$

6 tháng 8 2021

Bài 3 : 

a) $SO_3 + H_2O \to H_2SO_4$

b)

$n_{H_2SO_4} = n_{SO_3} = \dfrac{8}{80} = 0,1(mol)$
$C_{M_{H_2SO_4}} = \dfrac{0,1}{0,25} = 0,4M$

21 tháng 2 2023

MSC : `840`

`-5/8=-5.105/8.105=-525/840`

`7/10=7.84/10.84=588/840`

`-16/14=-16.60/14.60=-960/840`

`23/24=23.35/24.35=805/840`

`-1=-840/840`

Sắp xếp các phân số sau theo thứ tự giảm dần:

`805/840;588/840;-525/840;-840;-960/840`