Cho tứ diện OABC có OA, OB, OC đôi một vuông góc với nhau, và , . Gọi M là trung điểm của AB. Khoảng cách giữa hai đường thẳng OM và AC bằng           

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Một số câu hỏi khác có thể bạn quan tâm.

• Choose the word that has the underlined part pronounced differently from the rest:  

  many                   humanitarian                       friend                       weather

• Choose a word that has different stress pattern:

  interrupt                   international                       information                       intelligent

• Choose the best answer for the following sentence:

  I and my close friend are not in the same school now but we write ___________ regularly.
  
  

• Choose the best answer for the following sentence:

  _____________ money for her further study, she spent all her summer holiday to do a
  part-time job.
  
  

• Choose the best answer for the following sentence:

  Long: “Three new hotels _____________ in our city so far.”

  Thai: “What a good new!”
  
  

• Choose the best answer for the following sentence:

  Teacher: “You think that you came without __________ ?”

  Nam: “I’m sorry because I didn’t ask for your permission”
  
  

• Choose the best answer for the following sentence:

  He didn’t know what ___________ around him when he was sleeping.
  
  

• Choose the best answer for the following sentence:

  When he ___________ home he turned on the radio.
  
  

• Choose the best answer for the following sentence:

  ___________ do you prefer, Chemistry or Physics?

• Choose the best answer for the following sentence:

  The air-hostess had known that you were ill,_______________ ?