Tangent

Tangent is the trig function is the relation of the opposite side over the adjacent side. This is seen in the TOA part of SOH CAH TOA. Unlike the sin and cos functions of trig which are fairly similar in image, the graph of a tan line is completely different. The period of tangent is pi instead do two pi because the middle of the function goes up and through the origin. The graph also has vertical asymptotes so that each line is distinguishable. 

The graph goes infinitely up and down and cross the x-axis every pi instead of two pi as clearly shown in the picture above.