Giá trị \(\cot\dfrac{2\pi}{3}\) bằng
\(\dfrac{\sqrt{3}}{3}\) | |
\(-\sqrt{3}\) | |
\(-\dfrac{1}{\sqrt{3}}\) | |
\(-\dfrac{1}{2}\) |
Chọn phương án C.
Ta có \(\tan\dfrac{2\pi}{3}=-\sqrt{3}\).
Suy ra \(\cot\dfrac{2\pi}{3}=\dfrac{1}{\tan\tfrac{2\pi}{3}}=-\dfrac{1}{\sqrt{3}}\).