Solve a Trigonometric Equation!

Geometry

$\large 2^{1+3\cos x} - 10 \cdot 2^{-1+2\cos x} + 2^{2+\cos x} - 1 = 0$

If $x$ in the interval $0 \leq x < 2 \pi$ , find the sum of all possible values of $x$ satisfying the equation above.

Give your answer to 2 decimal places.