Tan((pi)/2) and tan-((pi)/2) tend to + infinity and - infinity respectively. So these are asymptotes when x=(pi)/6 and -(pi)/6 (+30 and -30 degrees). Tan0=0, tan((pi)/4)=1 and tan-((pi)/4)=-1 (x=(pi)/12 and -(pi)/12 (15 and -15 degrees) fix a few values of x to help you draw the graph. The points to plot are (-15,-4), (0,0), (15,4) as well as asymptotes at x=-30 and x=30. These values are within one cycle. At (0,0) the graph has a point of inflection so flattens out around the origin after rising from - infinity and before rising to + infinity. The graph takes on the same shape between x=30 to x=90, between x=-90 and x=-30, so the width of the cycle, or the period, is 60 degrees.