your graph i shown below:
this graph will repeat itself every 2*pi intervals on the x-axis.
this means that:
if you have a value at -pi/2, then you will have the same value at pi/2
if you have a value at -2p, then you will have the same value at 0 and you will have the same value at 2p.
the value of the equation at selected intervals is:
x value y value
-2pi -2/3
-pi +2/3
0 -2/3
pi +2/3
2pi -2/3
this graph will have asymptotes at:
x = -3pi/2
x = -pi/2
x = pi/2
x = 3pi/2
these asymptotes are represented by the vertical lines in the following graph of the same equation.
they may not look totally vertical, but they're as vertical as i can make them.