Cho sin anpha = 4/5. Tính cos anpha, tan anpha, cot anpha

* Hướng dẫn giải

$\begin{array}{l}\sin \alpha =\frac{4}{5}\Rightarrow {\cos }^2\alpha =1-{\sin }^2\alpha =1-{\left(\frac{4}{5}\right)}^2=\frac{9}{25}\Rightarrow \cos \alpha =\sqrt{\frac{9}{25}}=\frac{3}{5}\\ \tan \alpha =\frac{\sin \alpha }{\cos \alpha }=\frac{4}{5}:\frac{3}{5}=\frac{4}{3}\cot \alpha =\frac{1}{\tan \alpha }=\frac{3}{4}\end{array}$