Use a Calculator to Solve the Equation on the Interval $\cos 3 x = - \cos x$

Multiple Choice

Use a calculator to solve the equation on the interval [0, 2π) . Round the answer to two decimal places.
- $\cos 3 x = - \cos x$

A) $0.79,1.57,2.36,3.93,4.71,5.50$
B) $0,0.79,2.36,3.14,3.93,5.50$
C) $0,1.57,3.14,4.71$
D) $1.57,4.71$