Question

dado seno x 3/4 e x E 1º quadrante o cos x vale

Answer 1

$cos^2x + sen^2x = 1 cos^2x + \frac{9}{16} = 1 cos^2x = 1 - \frac{9}{16} = \frac{7}{16} \\ cos x= \frac{ \sqrt{7} }{4}}$