Cho hình chóp đều S.ABC cạnh đáy bằng a. Cạnh bên tạo với đáy góc
. Thể tích của khối chóp S.ABCD là:
A.A:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895744293_images/obj201744066538769895744293_img1.png)
B.B:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895490345_images/obj201744066538769895490345_img1.png)
C.C:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895806348_images/obj201744066538769895806348_img1.png)
D.D:
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895233462_images/obj201744066538769895233462_img1.png)
Đáp án và lời giải
Đáp án:C
Lời giải:Đáp án C
Gọi M là trung điểm BC, H là tâm ∆ ABC, ta có
Vì góc
nên
vuông cân tại H, suy ra
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img5.png)
![img6](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img6.png)
![img7](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img7.png)
![img8](https://cungthi.online/upload/questionbank3_20201220/eduquestion/201744066538769895/obj201744066538769895199534_images/obj201744066538769895199534_img8.png)