Cho(O,R) đường kính AB và dây AC không đi qua O. Gọi Hlaf trung điểm của AC a) tính góc ACB và chứng minh OH//BC b) Tiếp tuyến tại C của (O) cawts tia OH ở M. C/m: đường thẳng MA là tiếp tuyến tại A của (O) c) kẻ CK vuông góc AB tại K. Gọi I là trung điểm của CK và đặt góc CAB=α. Chứng minh Ck=2R.sinα d) Chứng minh M,I,B thẳng hàng
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
5 tháng 12 2023
a) Xét 2 tam giác ABE và ACF, ta có:
\(\widehat{AEB}=\widehat{ACF}=90^o\) và \(\widehat{A}\) chung
nên \(\Delta ABE~\Delta ACF\left(g.g\right)\) \(\Rightarrow\dfrac{AB}{AC}=\dfrac{AE}{AF}\) \(\Rightarrow AB.AF=AC.AE\) (đpcm)
b) Từ \(AB.AF=AC.AE\Rightarrow\dfrac{AE}{AB}=\dfrac{AF}{AC}\). Từ đó dễ dàng chứng minh \(\Delta AEF~\Delta ABC\left(c.g.c\right)\)
c) Kẻ đường kính AP của (O). Ta có \(\left\{{}\begin{matrix}AB\perp BP\\AB\perp HC\end{matrix}\right.\) \(\Rightarrow\) BP//HC
CMTT, ta có CP//HB, dẫn đến tứ giác BHCP là hình bình hành. Lại có A' là trung điểm BC \(\Rightarrow\) A' cũng là trung điểm HP.
Do đó OA' là đường trung bình của tam giác PAH \(\Rightarrow AH=2A'O\left(đpcm\right)\)
SV
Sinh Viên NEU
CTVVIP
5 tháng 12 2023
1. This book contributes little .......to........our understanding of the subject.
2. Children might benefit a lot ........from...... sharing housework with their parents.
3. Parents are recommended to collaborate ……with……………… teachers in educating children.
4. It is unfair to state that a woman’s job is to look ........after...... everyone in the family and takes care .......of....… the house
5. Parents should set good examples …………to………… their children.
6. Skeletal system of the body is made …………up.. ……………. our bones.
7. A healthy balance ……between……. work and play ensures that everyone has a chance to enjoy their lives.
8. He and his wife shared a passion ........for...... classical music.
9. I haven’t made …………up………… my mind yet.
10. This figure graduated .........from........... a very famous music school and devoted his life ……to…… arts.
SV
Sinh Viên NEU
CTVVIP
5 tháng 12 2023
1. Bill decided (buy) ..............to buy.............. a new car rather than a used one.
2. I really dislike (ask) ........being asked.................... personal question when I am on duty.
3. Gregory is a vegetarian. He ...............doesn't eat.......... (not/eat) meat.
4. I ..............am looking........... (1ook) for the manager. I can't find him anywhere.
5. We are successful because we ...............took.......... (take) the time to talk to our customers.
6. John ...............has dealt.......... (deal) with all the enquiries about sales.
7. At the moment we .............are making............ (make) a training video for Siemens.
8. How long ................has she studied......... (she/study) German?
9. When .....................did he begin.... (he/begin) to study Business Administration?
10. Who ................wrote......... ( write ) the play Dancing at Lughnasa.
11. ............Did you visit............. (you/visit) any museums when you were in Sofia
12. Henry has a perfect school record. He .........wasn't............. (not/be) sick this year.
13. Prices .................is going........ (go) up. Things are much more expensive this week
14. What ........happened................. (happen) to you. I waited all afternoon for you.
15. He ..................had....... already (go).....went.................... before I (come)..............came........... there.
SV
Sinh Viên NEU
CTVVIP
5 tháng 12 2023
16. After my sister (wash).........had washed................ her clothes she (begin)............began............. to study.
17. Bill ( work).............had worked............ at the University for 40 years before he ( retire)................retired.........
18. A: Oh. I’ve just realized. I haven’t got any money.
B: Haven’t you? Well, don’t worry...........I will lend............you some (I/lend).
19. A: I’ve got a headache. B: Have you? Wait there and...........I will get.........an aspirin for you.( I/get)
20. A: Why are you filling that bucket with water? B: ........I am going to wash ................. the car (I/wash)
21. While I ..................was having....... (have) a bath, someone .......knocked.................. (knock) on the door.
22. When I nearly reached the office, I suddenly .............remembered ............ (remember) I .........had forgot................ (forget) to turn off the gas stove.
23. Laura felt so tired that she .........fell................ fall) asleep on the sofa.
24. While Pat ..................was cleaning....... clean) the house, she ...........noticed.............. (notice) a secret door behind the wardrobe.
25. They had a good rest when all their guests ...............had left.......... (leave).
26. When ............did you last play............. you, last play) for the national team?
27. I ...........didn't listen..............(not, listen), so I missed what the teacher said.
28. It ..........rained............... (rain) hard all day yesterday.
29. James .............was driving............ (drive) home along a deserted street when he ................saw........ (see) a strange animal.
30. The robbers ............had run............. (run) away by the time the police..............arrived........... arrive).
TB
3
5 tháng 12 2023
Kết quả nhận dạng
\(y=\left(a-3\right)+5-a\)
Để giải phương trình này, ta cần thực hiện các bước sau:
1. Kết hợp các thuật ngữ giống nhau:
\(y=\left(a-3\right)+5-a\)
2. Rút gọn các thuật ngữ tương tự:
\(y=-3+5\)
3. Tính toán: \(y=2\)
Vậy câu trả lời là y = 2
PT
0
4 tháng 12 2023
a)Nối M và B bằng một vôn kế rất lớn.
Khi đó CTM là: \(\left(R_1//\left(R_2ntR_3\right)\right)ntR_4\)
Ta có: \(U_V=U_3+U_4\)
\(R_{23}=R_2+R_3=6+6=12\Omega\)
\(R_{123}=\dfrac{R_1\cdot R_{23}}{R_1+R_{23}}=\dfrac{6\cdot12}{6+12}=4\Omega\)
\(R_{tđ}=R_{123}+R_4=4+2=6\Omega\)
\(I_4=I_{123}=I=\dfrac{U}{R_{tđ}}=\dfrac{18}{6}=3A\Rightarrow U_4=I_4\cdot R_4=3\cdot2=6V\)
\(U_{23}=U_{123}=I_{123}\cdot R_{123}=3\cdot4=12V\)
\(I_2=I_3=I_{23}=\dfrac{U_{23}}{R_{23}}=\dfrac{12}{12}=1A\Rightarrow U_3=I_3\cdot R_3=1\cdot6=6V\)
Vậy \(U_V=U_3+U_4=6+6=12V\)
b)Nối M với B bằng một ampe kế lớn.
Khi đó CTM là \(\left(R_1nt\left(R_3//R_4\right)\right)//R_2\)
Ta có: \(I_A=I_2+I_3\)
\(R_{34}=\dfrac{R_3\cdot R_4}{R_3+R_4}=\dfrac{6\cdot2}{6+2}=1,5\Omega\)
\(R_{134}=R_1+R_{34}=6+1,5=7,5\Omega\)
\(R_{tđ}=\dfrac{R_{134}\cdot R_2}{R_{134}+R_2}=\dfrac{7,5\cdot6}{7,5+6}=\dfrac{10}{3}\Omega\)
\(U_2=U_{134}=U=18V\)
\(I_2=\dfrac{U_2}{R_2}=\dfrac{18}{6}=3A\)
\(I_{34}=I_{134}=\dfrac{U_{134}}{R_{134}}=\dfrac{U}{R_{134}}=\dfrac{18}{7,5}=2,4A\)
\(U_3=U_4=U_{34}=I_{34}\cdot R_{34}=2,4\cdot1,5=3,6V\)
\(I_3=\dfrac{U_3}{R_3}=\dfrac{3,6}{6}=0,6A\)
Vậy \(I_A=I_2+I_3=3+0,6=3,6A\)