a ) sin2 + cos2 = 1
\(\Rightarrow\) \(cos=\sqrt{1-sin^2}=\sqrt{1-0,36}=0,8\)
\(tan=\dfrac{sin}{cos}=0,75\)
\(cotg=\dfrac{1}{tan}=\dfrac{4}{3}\)
b ) Tương tự câu a
\(sin=\sqrt{1-cos^2}=\sqrt{\dfrac{5}{9}}\)
\(tan=\dfrac{sin}{cos}=\dfrac{\sqrt{5}}{2}\)
\(cotg=\dfrac{2}{\sqrt{5}}\)