SOLUTION: solve cos x/3 - sin x/3 = 0 over the interval [0, 2pi)

If   cos(x/3) - sin(x/3) = 0,  then

    cos(x/3) = sin(x/3),


which implies

    tan(x/3) = 1.


Hence,  x/3 =    and  x = .


In the interval  [0,2pi) the solution is unique :  x = .    ANSWER