Nghiệm của phương trình lượng giác
có nghiệm là:
A.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029963935_images/obj2019060484219180029963935_img1.png)
B.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029328995_images/obj2019060484219180029328995_img1.png)
C.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029582943_images/obj2019060484219180029582943_img1.png)
D.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029982332_images/obj2019060484219180029982332_img1.png)
Đáp án và lời giải
Đáp án:B
Lời giải:Chọn B
Ta có
Vì
nên chỉ có
thỏa mãn.
Vậy ta có:![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029697322_images/obj2019060484219180029697322_img4.png)
Vậy đáp án đúng là B.
![img1](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029697322_images/obj2019060484219180029697322_img1.png)
![img2](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029697322_images/obj2019060484219180029697322_img2.png)
![img3](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029697322_images/obj2019060484219180029697322_img3.png)
![img4](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029697322_images/obj2019060484219180029697322_img4.png)
![img5](https://cungthi.online/upload/questionbank3_20201220/eduquestion/2019060484219180029/obj2019060484219180029697322_images/obj2019060484219180029697322_img5.png)