The tan(α) function is a trigonometric functions that looks a bit different than sin(α) or cos(α). Its values can be between -∞ and ∞.

tan(α) > 0, for all α in (0°; 90°) and for all α in (180°; 270°)

tan(α) < 0, for all α in (90°; 180°) and for all α in (270°; 360°)

The tan function can be seen in the unit circe:

Tip: The equation tan(α) = sin(α) / cos(α) always holds.

Some important angles:

tan(0°) = 0

tan(180°) = 0

tan(360°) = 0

The tan(α) function can also be displayed in a coordinate system, shown in the picture below.

You can find a code example for the tan / arctan function here.