cosx=13⇒cos2x=19⇒sin2x=89Do 0<x<π2⇒sinx>0⇒sinx=2√23tanx=sinxcosx=2√2cotx=1tanx=12√2
$
\cos
x=\frac{1}{3} \Rightarrow
\cos^2x=\frac{1}{9}\Rightarrow
\sin^2x=\frac{8}{9}
Do0<x<\frac{\pi}{2}
\Rightarrow
\sin
x>0
\Rightarrow
\sin
x=\frac{2\sqrt{2}}{3}$$
\tan
x=\frac{\sin x}{\cos x}=2\sqrt{2}$$
\cot
x=\frac{1}{
\tan
x}=\frac{1}{2\sqrt{2}}$