Chứng minh rằng luôn có 1 tam giác mà diện tích của nó bằng diện tích của 1 tứ giác cho trước.

Giải giúp em bài này với ạ. Em cảm ơn Cho tứ diện ABCD có AB, AC, AD vuông góc từng đôi một. Gọi H là trực tâm tam giác BCD. Chứng minh AH vuông góc với (BCD)

giúp e mấy câu này vs ạ e cảm ơn

Bài này khó quá. Em mong các thầy cô giải giúp em bài này với ạ. Em cảm ơn các thầy cô rất nhiều ạ.

Viết chương trình nhập vào số nguyê. In ra màn hình số đó có mấy kí tự số.

Giúp giải câu này với mọi người

Vẽ xOy=60 độ và tia phân giác Ot.Lấy A,B thuộc Ox sao cho A nằm giữa O và B.Lấy C thuộc Oy sao cho OA=OC,AB=CD a)Tam giác OBD là tam giác gì? b)Tính số đo của OBD c)Chứng minh AC song song với BD

IX. Find the mistakes in the following sentences: 1. Any kind of violence must not be allow at school 2. These medicine must keep out of children’s reach 3. The instruction must follow strictly by the students 4. In the case of pupil being absent from school, messages can leave on the answering machine before 7:30 am 5. These pill must not take if you are under 12 years old. X. Give the correct form of the words in brackets: 1. She faced .............................. because she not only had few friends but also was unwelcomed in that area ( lonely ) 2. That a woman becomes a ..................... has ever been considered to be weird, as people have assumed that this job is only for men ( firefight ) 3. Although she was aware of gender .................. in favor of boys, she applied for that position ( prefer ) 4. This university is ranked as one of the most successful institutions which have made ................. progress in gender equality ( consider ) 5. in order to eliminate gender inequality, domestic ................. need to be shared by both husband and wives ( responsible ) 6. The number of female ................... has increased sharply for the past few years ( enroll ) 7. My uncle is very .................... about rhinos. He has studied about them for a long time ( knowledge ) 8. By knowing their children’s strength and .................. parents can find appropriate strategies to educate them( weak ) 9. She contributed to the information of an ....................... for female pilots, gave advice to women on careers and helped inspire others ( organize ) 10. Even today, her life and career remain .................. to many people ( fascinate ) XI. Rearrange the words / phrases to make meaningful sentences: 1. equality / essay / an / gender / on / be / written / must / by / student / each 2. processed / will / when / these / files / be ? 3. a / course / finished / must / in / a / maximum / be / of / weeks / four 4. serious / obesity / be / health / considered / be / to / a / problem / can 5. achievements / in / information / technology / and / will / made / be / scientists / mor / by

VII. Finish each of the following sentences in such a way that it means the same as the sentence printed before it. 1. Somebody has to pick the visitors up from the airport ( up )  The visitors ......................................................................... from the airport 2. Why don’t they tell me about these changes earlier ? ( should )  I ..................................................................................... about these changes earlier/ 3. Luckily it wasn’t neccessary for Jim to take the exam again ( need )  Luckily Jim ..................................................................... the exam 4. In the end I had no choice but to get a lift with a colleague ( could )  In the end all ............................................................................. get a lift with a colleague 5. By law, all rear-seat passengers are obliged to wear seat-belts ( have )  By law, seat-belts ...................................................................... all rear-seat passengers 6. It may seem strange but I like stake cake ! ( as )  Strange ................................................................ I like stake cake ! 7. Visitors to the zoo are not allowed to feed the animals ( must )  The animals .......................................................by visitors to the zoo 8. I would have been better If he had told us his new address ( should )  He .................................................................................. his new address 9. Alice’s face turned bright red when the teacher asked her a question ( have )  Alice ................................................................................. embarrassed 10. The notice says you have to sign the form twice ( be )  The notice says the forms ............................................................. twice. VIII. Finish each of the following sentences in such a way that it means the same as the sentence printed before it. 1. It’s not neccessary for you to do the test  You .................................................................................................... 2. Nobody can deny that she has a beautiful voice  It ............................................................................................. 3. They will catch all the prisoners again tonight  all the prisoners ........................................................................ 4. They haven’t cleaned the street this week  The streets ....................................................................................... 5. He could repair the broken vase  The broken vase .............................................................................................. 6. The could not trace who had supplied the information in the first place  The course ......................................... 7. I gave Tom the message, but he already knew about it  I needn’t ....................................................................... 8. It’s a pity you didn’t come to the party because you’d have loved it  You .......................................................... 9. It is essential that no one be told about our plans  You ....................................................................................... 10. It was wrong of you not to call the doctor at once  You ....................................................................................

sao chương trình mình không chạy được ạ