To find coterminal angles, add (or subtract) multiply of 2·pi
Therefore, angles coterminal with 2·pi/3 are
2·pi/3 + 2·pi, 2·pi/3 + 4·pi, 2·pi/3 + 6·pi,, ...
and 2·pi/3 - 2·pi, 2·pi/3 - 4·pi, 2·pi/3 - 6·pi,, ...
[you should reduce each answer]
Similarly, for -11·pi/7
