Trong không gian với hệ tọa độ
, cho đường thẳng
và mặt cầu
. Hai mặt phẳng
và
chứa
và tiếp xúc với
. Gọi
là tiếp điểm. Tính độ dài đoạn thẳng
A.A.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792204733_images/obj201735128697364792204733_img1.png)
B.B.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792790214_images/obj201735128697364792790214_img1.png)
C.C.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792139813_images/obj201735128697364792139813_img1.png)
D.D.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792378300_images/obj201735128697364792378300_img1.png)
Đáp án và lời giải
Đáp án:B
Lời giải:Đáp án B
Mặt cầu
có tâm
Đường thẳng
nhận
làm vectơ chỉ phương
Gọi H là hình chiếu của I lên đường thẳng d .
Lại có :
Suy ra tọa độ điểm
.
Vậy
Suy ra:
Gọi
là hình chiếu vuông góc của
lên đường thẳng
.
Suy ra:
.
Suy ra:
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img5.png)
![img6](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img6.png)
![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img7.png)
![img8](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img8.png)
![img9](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img9.png)
![img10](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img10.png)
![img11](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img11.png)
![img12](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img12.png)
![img13](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img13.png)
![img14](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img14.png)
![img15](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img15.png)
![img16](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201735128697364792/obj201735128697364792517870_images/obj201735128697364792517870_img16.png)