in the drawing above, is drawn part of the diagram of the tangent function. Please keep in mind that in order to get the complete diagram, you have to repeat my drawing infinity times on right and infinity times on left, since the function of tangent is a periodic function, and its period is equal to 3.14159...

Furthermore, the lines whose equations are x= pi/2 and x= - pi/2 are called the asymptotes of the function