Đường thẳng
đi qua
cắt
;
tại
,
sao cho
là trung điểm của
. Khi đó độ dài
bằng
![img1](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img1.png)
![img2](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img2.png)
![img3](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img3.png)
![img4](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img4.png)
![img5](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img5.png)
![img6](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img6.png)
![img7](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img7.png)
![img8](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img8.png)
![img9](https://cungthi.online/upload/questionbank3/eduquestion/20185421607315801659/obj20185421607315801659804594_images/obj20185421607315801659804594_img9.png)
A.
B.
C.
D.
Đáp án và lời giải
Đáp án:D
Lời giải:
Phân tích: Dễ thấy tam giác vuông tại
suy ra
.
Đáp án đúng là D