Question

Resolva a equação com x € [0,2π): 4 cos^2 x = 1​

Answer 1

$4cos^2x~=~1\\\\\\cos^2x~=~\frac{1}{4}\\\\\\cos(x)~=~\pm\sqrt{\frac{1}{4}}\\\\\\\boxed{cos(x)~=~\pm\frac{1}{2}}$

No intervalo [0,2π), cos(x) vale (+/-)1/2 para os ângulos:  $\frac{1}{3}\pi~,~\frac{2}{3}~,~\frac{4}{3}~,~\pi\frac{5}{3}\pi$