The relation defined by

*y*= arc tan(*x*) is not a function.### Notation

The symbol used to refer to the arc tangent of a real number *x* is “arc tan(*x*)” which is read as “arc tangent of x.”

### Examples

In the sexagesimal system of measuring angles, we have:

arc tan(1) = 45

arc tan(1) = 180n ± 45 where n is an integer.

- arc tan(1) = 45
- arc tan(1) = 180
*n*± 45 where*n*n is an integer.

Because tan(45°) = 1, arc tan(1) = 45.

It is the same for all angles from “45° ± 180°.”