Cho hình chóp
có đáy là hình vuông cạnh
,
. Hình chiếu vuông góc
của
lên mặt
là trung điểm của đoạn
. Gọi
là trung điểm của
. Tính khoảng cách giữa hai đường thẳng
và
theo ![img12](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img12.png)
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img5.png)
![img6](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img6.png)
![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img7.png)
![img8](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img8.png)
![img9](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img9.png)
![img10](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img10.png)
![img11](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img11.png)
![img12](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019463176248303705/obj2019463176248303705343433_images/obj2019463176248303705343433_img12.png)
A.
B.
C.
D.
Đáp án và lời giải
Đáp án:B
Lời giải:
Phân tích: Ta có:
. Dựng
khi đó
.
;
.
.
Vậy đáp án đúng là B.