Cho
. Tính
theo
.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20193628890216783422/obj20193628890216783422783422_images/obj20193628890216783422783422_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20193628890216783422/obj20193628890216783422783422_images/obj20193628890216783422783422_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/20193628890216783422/obj20193628890216783422783422_images/obj20193628890216783422783422_img3.png)
A.
B.
C.
D.
Đáp án và lời giải
Đáp án:A
Lời giải:
Phân tích: Ta có . Khi đó:
.
Đáp án đúng là A