306

$\cos x=\frac{1}{4}$
$\cos^2x+\sin^2x=1$
$\sin x=\pm\sqrt{1-\frac{1}{16}}$

$\sin x=\pm0{,}9682...\approx\pm0{,}97$

$\tan x=\frac{\sin x}{\cos x}=\frac{\pm0{,}9682...}{\frac{1}{4}}=\pm3{,}872...\approx3{,}87$