[Mức độ 1] Cho tam giác
vuông tại
, có
và
. Quay đường gấp khúc
quanh cạnh
tạo thành hình nón tròn xoay. Tính diện tích xung quanh
của hình nón đó.
A.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320813278_images/image202051232425532274320813278_img1.png)
B.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320735762_images/image202051232425532274320735762_img1.png)
C.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320193869_images/image202051232425532274320193869_img1.png)
D.
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320116353_images/image202051232425532274320116353_img1.png)
Đáp án và lời giải
Đáp án:A
Lời giải:Lời giải
Chọn A
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320608788_images/image202051232425532274320608788_img1.png)
Ta có:![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320782285_images/image202051232425532274320782285_img1.png)
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320704770_images/image202051232425532274320704770_img1.png)
. Vậy
.
Chọn A
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320608788_images/image202051232425532274320608788_img1.png)
Ta có:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320782285_images/image202051232425532274320782285_img1.png)
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320955783_images/image202051232425532274320955783_img1.png)
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320704770_images/image202051232425532274320704770_img1.png)
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320732827_images/image202051232425532274320732827_img1.png)
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/202051232425532274320/image202051232425532274320336374_images/image202051232425532274320336374_img1.png)