Question

dados cos x=4/5,com 0<x<pi,calcule a tg x e sex x?

Answer 1

$sen^2x + cos^2x = 1$
$sen^2x +( \frac{4}{5}) ^{2} = 1$
$sen^2x =1- \frac{16}{25}$
$sen^2x = \frac{9}{25} = senx = \frac{3}{5}$

$tgx = \frac{senx}{cosx}$
$tgx = \frac{ \frac{3}{5} }{ \frac{4}{5} }$
$tgx = \frac{3}{4}$