Question

sabendo que Senx = 3/4, com 0<x<Pi/2, calcule cosx. Use a relação sen²x + cos²x=1

Answer 1

$sen^2x+cos^2x=1 \\ \\ cos^2x=1-sen^2x \\ \\ cos^x=\sqrt{1-sen^2x} \\ \\ cos x=\sqrt{1-\left(\frac{3}{4}\right)^2} \\ \\ cos x=\sqrt{1-\frac{9}{16}} \\ \\ cos x =\sqrt{\frac{7}{16}} \\ \\ \boxed{cosx=\frac{\sqrt7}{4}}$