Question

Se 4senx+1=0, ache cos X.

Answer 1

$sen(x) = -\frac{1}{4} \\ \\ sen^2(x) + cos^2(x) = 1 \\ \\ (-\frac{1}{4})^2 + cos^2(x) = 1 \\ \\ cos^2(x) = 1 - \frac{1}{16} \\ \\ cos^2(x) = \frac{15}{16} \\ \\ cos(x) = \frac{ \sqrt{15} }{4}$