Here,
#tan^2x=1/3=(1/sqrt3)^2, where, 0 <= x <= 2pi#
#=>tanx=+-1/sqrt3#
Now,
#(i) tanx=1/sqrt3 > 0=>I^(st)Quadrant or III^(rd)Quadrant#
#:.x=pi/6to I^(st)Quadrant or#
#x=pi+pi/6=(7pi)/6toIII^(rd) Quadrant#
#(ii)tanx=-1/sqrt3 < 0=>II^(nd)Quadrant or IV^(th)Quadrant#
#:.x=pi-pi/6=(5pi)/6toII^(nd)Quadrant or#
#x=2pi-pi/6=(11pi)/6to IV^(th)Quadrant#
Hence,
#x=pi/6,(5pi)/6,(7pi)/6and(11pi)/6#