Question

Se sen x= 3/5, com x E 4º quadrante, então tg x é: 
a) -3/4
b)3/4
c) -4/3
d) 1/2
3) 4/5

Answer 1

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

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

Sendo do 4o. quadrante tg x = -3/4