Cho tam giác ABC ,đường cao BE,CF cắt nhau tại K. Gọi O là trung điểm của BC, I là điểm đối xứng với K qua O.
a .Chứng minh AB vuông góc với BI
B .Chứng minh AE.AC = AF.AB ,BF.BA=BE.IC.
C .Gọi N là trung điểm của AI.Chứng minh rằng N là giao điểm các đường trung trực của tam giác ABC.
1. Cho hình chóp tam giác đều có bán kính đường tròn ngoại tiếp đáy bằng \(2\sqrt{3}\) , chiều cao hình chóp bằng \(5\sqrt{3}\). Tính thể tích
2. Cho hình chóp tứ giác đều, cạnh đáy bằng 8cm, chiều cao bằng 10cm. Tính diện tích xung quanh, thể tích.
3. Cho hình chóp tứ giác đều, cạnh đáy bằng 6cm, cạnh bên bằng 5cm. Tính diện tích xung quanh, diện tích toàn phần, thể tích.
4. Cho hình chóp tứ giác đều S.ABCD có AB = 10cm, SA = 12cm. Tính AC, SO, CO (O là giao điển AC với BD), thể tích.
Cho dạng đúng của từ trong ngoặc:
1. Explosives are _________ weapons. (DIE)
2. We feel that you have been _______ and that you are to blame. (NEGLECT)
3. We were impressed by the ________ use of light and shade in the painting. (IMAGINE)
4. Something that is ______cannot burn or is very diffucult to burn. (FLAME)
5. Are all these _______they put in food really necessary? (ADD)
I. Chọn đáp án thích hợp nhất để hoàn thành các câu sau:
1. We just take it as ______ that anyone who applied for the couse would have the necessary qualifications.
A. Usual
B. Work
C. Fixed
D. Read
2. My mother had to work 12 hours a day in a factory just to _______
A. Make ends meet
B. Call it a day
C. Break the ice
D. Keep a living
3. In a formal interview, it is essential to maintain good eye ________ with the interviewers.
A. Link
B. Contact
C. Shortage
D. View
4. The village was __________ visible through the dense fog.
A. Mostly
B. Hard
C. Only
D. Barely
5. Laura had a blazing ______ with Edie and stormed out of the room.
A. Chat
B. Gossip
C. Row
D. Word
6. Like most models, she has a lovely ____
A. Build
B. Figure
C. Physique
D. Form
7. The fact that my friend and I bought the same dress was _____ coincidence.
A. Bare
B. Simple
C. Basic
D. Sheer
8. China’s placement of its oil rig in Vietnam’s East Sea EEZ was denounced by ASEAN and Western politicians and professionals as the violation of Vietnam’s ____ waters.
A. Farmed
B. Fresh
C. Inland
D. Territorial
9. Nothing _______ the ordinary ever happens here.
A. About
B. Out of
C. From
D. Within
10. Clouds can be classified into family groupings according to their height and shape.
A. Distributed
B. Registered
C. Specified
D. Categorized
Chia từ loại trong ngoặc:
1. Information technology has developed (ENCOURAGE).......... in vietnam in recent years.
2. Various kinds of colorful flowers were used to (BEAUTIFUL) ............... the stage in the Opening ceremony to receive cultural events ò Bac Giang province"
3. (CERTAIN)........... about the company's future meant that few people wanted to invest money on it.
4. This is the first time in vietnam that the party politburo and its members' mistakes have been (PUBLIC)............
5. You should use it as a study room. It's (COMPARE) ............. quite.
6. They were brought up to behave in a (CIVILIZATION)......... way in public.
7. Fruit (SWEET)............ as it ripens.
8. He is very (SYSTEM)............ in everything he does.
9. He wrote so many (GRAMMAR).......... sentences in his essay.
10. They daren't leave their children (ATTEND).............. for even a moment.
15 x 3 = 45