Cho khối chóp S . A B C D có đáy là hình chữ nhật cạnh A D = 2 a ,   A D = a  Hình chiếu của đỉnh S lên đáy là trung điểm của cạnh  AB cạnh bên SC tạo với mặt phẳng đáy một góc 45 0  Tính thể tích V của khối chóp đã cho.

Thầy ửi tain sao câu hỏi em mới đăng xong mà không tìm thấy mà nhìn toán thấy mấy câu hỏi từ tháng 5, 6 ở mục mới nhất là sao thầy

15 phút = 1/4 giờ

Quãng đường từ nhà đến trường: 15x1/4=15/4 (km)

Thời gian về Lan muốn là: 15-3=12 (phút)

Vận tốc cần đi lúc về trong thời gian Lan muốn là: 15/4:12=5/16 (km/giờ)

2. 

Dan is a young girl with a small frame with pale skin, smooth. Oval face with innocent eyes of a child, Dan always soften the hearts of many with just a glance. The berry red lips, mouth smile always fresh to reveal white teeth, seemed pearls. This girl has design flexible, gentle. The voice sounded very sweet and gentle. Thus in each of the singing competition, your presence was indispensable. Vocalist "homegrown" This has brought about the class, the school a lot of the first, second. Knitting class when it seems very gentle, easygoing but learning very seriously. The operation of the school, then you are always topped the class. However, Denmark is still regarded as the most necessary learning. With a head smart and fast calculation, so you are very good at math. Dan has always been my teachers and friends to study well liked by helpful friends. Home, outside school hours, Dan always made time to help their parents.

Hobbies reading, knitting has a somewhat bizarre hobby is like to watch Ghost. Every spare time is two to inquire about learning, fun confided sad story. Time that you have a cold, Dan has demonstrated his is indeed a good friend. I had to leave school every two weeks. However Denmark still to your house and teach you each problem, post office. This made me really makes me emotional. When my wife was sick at two walk together on the way to school. Print path happy memories, sad friends.

Dan has always been a good friend not only for me but for everybody. I'll try to do well for you two are best friends forever, sometimes you come forward.

5. Do you agree that the study of Mathematics is essential to the progress of the human race?

Though the study of Mathematics had occupied the attention of Egyptian and Greek scholars centuries ago, yet it was only after the advent of the Industrial Revolution that the importance of the subject was fully realised by scholars and educationists everywhere. Today, Mathematics is one of the most important subjects in all the schools and universities of the world. 

Before the Industrial Revolution, men lived very simple lives. Agriculture, hunting and fishing were then their main sources of livelihood. It did not occur to them that their lives could be made more comfortable if they only exercised their mental faculties a little more and organised a system of knowledge, which we now call the Science, and applied it to practical purposes. Thus, they turned to nature for sustenance, and were satisfied with what they could acquire from nature with their skills. This simple mode of existence was, however, disturbed by the inventions of a few men, sometime in the eighteenth century, which caused people everywhere to think of new ways of improving their conditions of living. The inventions revealed new sources of comfort, and power for the production of goods. Thus, the Industrial Revolution began. More and more machines were invented for the rapid production of goods, and the study of Mathematics began to receive great encouragement, for it was realised that machines function on mathematical principles. 

The intensive study of Mathematics revealed its potentialities. It was soon applied not only to invent new machinery but also to explain abstruse subjects such as Physics, Logic and many others. In fact, Mathematics is now used to teach and explain almost every important subject in schools and universities. Even the construction of buildings and bridges requires a deep knowledge of Mathematics. 

The study of Mathematics has also helped to increase the mental powers of men. They are not only able to think more clearly than they could before but are also able to understand and explain many of the things which they could not understand earlier. 

Sometimes, however, Mathematical principles have been applied for tragic consequences. In battles and wars, bombs and cannon-balls have been released with remarkable accuracy to destroy the enemy. This fact reveals how knowledge of Mathematics could be used to hinder human progress. But such a situation develops only when men have lost their patience and their capacity for compromise and fortunately the leaders of the world today are trying their utmost to remove the causes for war. 

In general, however, men have a natural impulse to live in peace and harmony with others, and almost every invention is aimed at promoting the welfare of the peoples of the world. Thus, the human race has benefited from the efforts of those who have made the fullest use of Mathematical principles for all their inventions. I therefore agree that the study of Mathematics is essential to the progress of the human race

3. Everyone has a dream of his, who are estimated to make pay the army, the Convention as a teacher, the Convention as a pilot. And I also have my dream. My dream is to become a writer.
When I tell people about this dream, many people believe that you're the romantic. A writer would have to have a romantic soul, said observers, emotional life, in harmony with everyone. From childhood I have read books by Nguyen Nhat Anh uncle, great uncle was writing, I was fascinated by how to write simple but affectionate of him.
Then I also want to become a writer, could be going to a lot of places, met many people, visited many places and can start writing. Perhaps when that emotion will very much and I will have work or. If you are a writer, then I'll become a celebrity, is well known, they will have their own books, can bring people come to show off your product.
Because being a writer dreams should from now you must read a lot, write a lot, then this could well be written. I admire writers, poets because they have a spiritual life is very rich. They beauty of life in these pages, and you also want to become like that.
I like freedom, like flying, so I do not like having to sit around. I think as a writer to go much, much new life with the good and meaningful work. I will try harder to be able to achieve his dream.
Whatever path you go there very long but I think if everyone has dreams, try and strive to know, they will surely do. I wanted to write the book about family, friendship, love, life. I will win donated three, gave my mother because they were always beside me, trying to motivate me to study well.
I will try to achieve that dream.

1. Tall about your school

Talk about your school My school There is a white three-storey building, surrounded by greenery, located at Simei Town Central. That is Simei Primary School. That is also the place where I have schooled for the last five years or so. My school uniform is white. The boys wear a white shirt and white shorts while the girls wear a white blouse and skirt. The uniform must always be worn with the school badge which bears our school motto “Nothing without labor”. It means that we must be willing to work to get our reward. We are also taught to be honest and polite all the time. Most of the teachers in my school are just and kind. However, there are some teachers who show favoritism. As a result, the students who are favored by these teachers are very proud and like to bully the others. In general, however, we all treat one another like siblings and live in harmony. I am sad that I will have to leave my school at the end of this year. It has given me knowledge, friends and happy moments. I will always remember my school and the fond memories it holds. Describe your school. I study in XYZ Secondary School. It is one of the best schools in Singapore. It consists of several Roman style buildings. Our school has all the facilities of a modern school, such as well furnished and airy class rooms, best laboratories, a big library with a huge collection of books, a vast play ground and even a swimming pool. Our school building is situated in the middle. There is motorway leading from the main entrance. The playground is on the left of the motorway and a big garden on the right. When you enter the building, the principal’s room is on the left. They are all well furnished. There are twenty classrooms. Our laboratories are well equipped. The school library has an up-to-date collection of books on many subjects. Our librarian and her two assistants are very helpful. Our school, like other schools, has prescribed a uniform for us. We have to wear white trousers, a white shirt and a black tie. The girls have to wear white shirts and skirts.Our principal is very strict as he pays strict attention to behavior, punctuality and cleanliness. The most well- behaved and punctual student will be assigned as the class prefect. Our principal is a strict disciplinarian. He accepts the help and advice of all teachers. Though our principal is strict, he is fair and loving. He tries to find out the reason and guides us. If one violates any rules, he will be punished. Our principal is very strict in this aspect.Our teachers are also very strict. They teach us with the utmost care, guide us with our assessments and other preparations and help us in times of need. I like my school very much and am proud to be a student of that school.

Exercise 1:

1. I visited Bana Hills last summer.

2. They went skiing three months ago.

3.Nam is doing homework at the moment,

Exercise 2:

1. I like the living room best in my house.

2. How about going to Sa Huynh Coffee tonight?

3. You mustn't tallk too much in the class.