Question

[Kayla Phuong]

a) Cho \(\sin\alpha=-\frac{3}{5}\left(\pi< \alpha< \frac{3\pi}{2}\right)\). Tính tan \(\alpha\)=?

b) Cho \(\alpha=\frac{\sqrt{3}}{3}\left(90^0< \alpha< 180^0\right)\). Tính cot \(\alpha\)=?

Answer 1

[Nguyễn Việt Lâm]

\(\pi< a< \frac{3\pi}{2}\Rightarrow\left\{{}\begin{matrix}sina< 0\\cosa< 0\end{matrix}\right.\)

\(\Rightarrow cosa=-\sqrt{1-sin^2a}=-\frac{4}{5}\) \(\Rightarrow tana=\frac{sina}{cosa}=\frac{3}{4}\)

b/ \(sina=\frac{\sqrt{3}}{3}???cosa=\frac{\sqrt{3}}{3}???\)