This answer would be best shown using a diagram. However you must ensure that the graph crosses the x axis at -180, 0 and 180 degrees. Moreover it is also necessary that the student has included asymptotes which have equations x=90 degrees and x=-90 degrees. Finally the graph need to show that for -180 =< x < -90, -90 < x < 90 and 90 < x =<180 it is an increasing function however the gradient varies and this will better be shown in a diagram.