Cho tam giác ABC cân tại A nội tiếp đường tròn tâm O . Đường cao AH cắt đường tròn ở điểm D. a) AD có phải là đường kính của đường tròn tâm O không ? Tại sao? b) Chứng minh BC ^2 = 4AH . DH c) Cho BC= 24cm, AB=20cm. Tính bán kính của đường tròn tâm O.

giai cấp công nhân việt nam dưới cuộc khai thác thuộc địa lần 2 chuyển biến ra sao

cho tam giác ABC cân tại A đường cao thuộc cạnh bên bằng H góc đáy bằng alpha chứng minh rằng: Sabc=H^2 phần 4 nhân sin alpha nhân cos alpha

X. Fill in each blank with a proper expression of quantity. Use of where necessary. 1. I feel lonely here because I have _______________________ friends in this city. 2. These books are all Jane’s. _______________________ them belong to me. 3. Not all the people I work with are very friendly. ___________________ them are unfriendly at all. 4. Are those people English? No, just _______________________ them. 5. _______________________ schools open in September. 6. Let’s go and have a drink. We’ve got _______________________ time before the train leaves. 7. Have you got ______________ money? ~ Yes, but not _______________________. 8. Hurry or we’ll be late. We have very _______________________ time. 9. I have done _______________________ the exercises of grammar in this book, so I’m going to buy another book. 10. We all got wet in the rain because _______________________ us had an umbrella. 11. We’ll have to work quickly because I haven’t got _______________________ time. 12. I do not know __________________ about biology, but I have ___________________ knowledge about genetics. 13. The librarian says that you may borrow as _______________________ books as you want to. 14. The boys are making too _______________________ noise. 15. I watched _______________________ the film but not all of it. 16. I’m very poor. I have _______________________ money. But my brother is richer than I. He has _______________________ money in the bank. 17. Before mixing the cake, weight _______________________ ingredient precisely. 18. When my rich uncle died, he left _______________________ his fortune to his cat. He hadn’t left _______________________ it to us. 19. How ______________________ languages can you speak? And how _______________________ time do you spend on learning English? 20. When my rich uncle died, he left _______________________ his fortune to his cat and the other half to a distant cousin! We had never expected to receive _______________________ it, but we were disap¬pointed that he hadn’t left _______________________ it to us.

Giải hộ mik bài 1,2,3 nha Mik đang cần gấp Cảm ơn trc nha

bài 2 : tìm 3 STN liên tiếp biết rằng tổng của chúng là 75 cảm ơn nha hihihihihih

Chào mng cho mình hỏi là tại sao khi phân tích đa thức bằng cách đặt nhân tử chung thì nên chọn ƯCLN cho phần hệ số và biến lấy số mũ nhỏ nhất vậy ạ tại sao ko phải là BCNN em cảm ơn.

1Ann is very tired . she _____ tennis for three hours A:is playing B:will play C:plays D:has been playing 2 he works in a bank, but he ______ it very much A:doesn't enjoy B:haven't enjoy C:đin't enjoy D:hadn't enjoy 3 I ____ well lattely.Mabe I should go to the doctor A: didn't feel B:won't feel C:haven't been fee;ing D:am not feeling 4 I _____ my homework for two hours,but I ____ yet A:have done-haven't finished B:is doing-isn't finishing C:will dp-will not finish D:have been doing-haven't finished 5let's take our travel chess set in case wwe _____ bored on the train A:Get B:are getting C:got D:have got 6 we ____ get in touch with our customers by post A:recently B:hardly C:lately D:latterly 7 We have been married ______ A:over twenty years B:over twenty years ago C:for over twenty years D:since over twenty years 8 melanie ______- her hand. It's bleeding heavily A:has cut B:is cutting C:cut D:cuts 9" when will Mary be able to leave hosptal?" - "Don't be so impatien. we cannot realease her before we ________ the last test A:have complete B:will have completed C:will complete D:completed 10 The Amazon river____ into the Atlantic Ocean A:flows B:has flowed C:is flowing D:will flow 11 My parents live in London. They _______ there all their lives A:are living B:had lived C:have lived D:will live 12 where have you been? I ____ for you the last half hour A:am looking B:have been looking C:will be looking D:look 13 My brother is an actor. He ______ in several movies A:appeared B:had appeared C:has appeared D:appears 14 Please don't bother hom now. he ________ A:is working B:has been working C:had been working D:was working 15 I _______ an interesting book at the moment. I will lend it to you when I ____ it A:am reading - have finished B:read - am finishing C:have read - am finishing D:read -will finish 16 Ha never ______ fishing in the winner but she always ___-it in the summer A:goes-does B:has gone - done C:go - do D: was gone - done 17 we can win only if we remain united, so we must suppor them the moment they_____ on strike A:will have gone B:will go C:go D:went 18 I am sr . i ______ that fellow's name already A:forgot B:have forgotten C:have been forgetting D:forget 19It usually ______ very much in that part of the United States A:is rainning B:rained C:rains D:have rained 20 look! A man _____ after the train. he wants to catch it A:runs B:have been running C:will run D:is running

so sánh: C=3^10+1/3^9+1 và D=3^9+1/3^8+1

Tổ chức cộng sản ra đời đầu tiên ở nước ta là tổ chức nào ???