Find All Solutions to the Equation $$\cos ^ { 2 } x = 0.8$$

Find all solutions to the equation.
- $$\cos ^ { 2 } x = 0.8$$
(Use a calculator. Express your answer in radians as a decimal rounded to the nearest thousandth.)

A) $\{ 0.464 + 2 \mathrm { n } \pi , 5.819 + 2 \mathrm { n } \pi \mid \mathrm { n } = 0 , \pm 1 , \pm 2 , \ldots . \}$
B) $\{ \pm 0.644 + \mathrm { n } \pi \mid \mathrm { n } = 0 , \pm 1 , \pm 2 , \ldots . \}$
C) $\{ 0.644 + 2 \mathrm { n } \pi , 5.639 + 2 \mathrm { n } \pi \mid \mathrm { n } = 0 , \pm 1 , \pm 2 , \ldots . \}$
D) $\{ \pm 0.464 + \mathrm { n } \pi \mid \mathrm { n } = 0 , \pm 1 , \pm 2 , \ldots \}$