题目内容

(本题满分15分)

  在三棱锥中,

(1)证明:

(2)求三棱锥的体积

 

 

 

 

【答案】

(1)证明:

              ∴

             ……………………………………………………2分

               所以  ……………………………………………………4分

              又所以……………………………………6分

              ∴ …………………………………………………8分

              ∴ …………………………………………………………10分

 (2)在中, 所以, ………12分

      又 在中,所以  ………14分

       又所以………15分

 

【解析】略

 

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