Cho \(\sin \alpha  = \frac{1}{{\sqrt {10} }},\,\,\left( {0...

* Hướng dẫn giải

\(\begin{array}{l}
{\sin ^2}\alpha  + {\cos ^2}\alpha  = 1 \Leftrightarrow {\cos ^2}\alpha  = 1 - {\sin ^2}\alpha  = \frac{9}{{10}}\\
 \Rightarrow \cos \alpha  = \frac{3}{{\sqrt {10} }},\,\,\tan \alpha  = \frac{1}{3}
\end{array}\)