Question

Dado sen x = 3
/5
e 0 < x <
/2

, qual o valor de cos x ?​

Answer 1

Relação fundamental da trigonometria:

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