# Documentation/Calc Functions/ATAN

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## Function name:

ATAN

## Category:

Mathematical

## Summary:

Returns the inverse trigonometric tangent (the arctangent) of a number. This function calculates the principal value.

## Syntax:

ATAN(**Number**)

## Returns:

This function returns the inverse trigonometric tangent of **Number**, that is the angle (in radians) whose tangent is **Number**. The angle returned is between -PI/2 and PI/2, i.e. [-π/2,+π/2].

## Arguments:

**Number** is the real number, or a reference to a cell containing that number whose inverse trigonometric tangent value is to be calculated.

## Additional details:

- To return the angle in degrees, use the DEGREES function.
- Alternatively multiply by 180/PI() to convert the result from radians to degrees.

The figure below illustrates the function ATAN.

## Examples:

Formula | Description | Returns |
---|---|---|

=ATAN(1) | Inverse trigonometric tangent of 1 | 0.785398163397448 (PI/4 radians or π/4) |

=ATAN(0.5) | Inverse trigonometric tangent of 0.5 | 0.463647609000806 (radians) |

=DEGREES(ATAN(1)) | Inverse trigonometric tangent of 1. Further, converting angle in radians to degrees. | 45° (degrees) |

=ATAN(-1)*180/PI() | Inverse trigonometric tangent of -1. Further, converting angle in radians to degrees by multiplying by 180/PI(). | -45° (degrees) |

## Related LibreOffice functions:

## ODF standard:

## Equivalent Excel functions:

ATAN