Ta có: \({\sin ^2}\alpha + {\cos ^2}\alpha = 1\)
Suy ra: \({\sin ^2}\alpha = 1 - {\cos ^2}\alpha = 1 - {(0,8)^2}\)\( = 1 - 0,64 = 0,36\)
Vì \(\sin \alpha > 0\) nên \(\sin \alpha = \sqrt {0,36} = 0,6\)
Suy ra: \(\tan\alpha = \dfrac{{\sin \alpha }}{{\cos \alpha }} = \dfrac{{0,6}}{{0,8}} = \dfrac{3}{4} = 0,75\)
\(\cot\alpha = \dfrac{1}{{\tan\alpha }} = \dfrac{1}{{0,75}} = 1,3333\)
