# Documentation/Calc Functions/ATAN

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## Function name:

ATAN

## Category:

Mathematical

## Summary:

Calculates the inverse trigonometric tangent (arctangent or arctan) of a real number. The value returned is the principal value and lies in the range (-π/2, π/2) radians.

## Syntax:

ATAN(**Number**)

## Returns:

Returns a real number in the range (-π/2, π/2) that is the inverse trigonometric tangent of **Number** in radians.

## Arguments:

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

- If
**Number**is non-numeric, then ATAN reports a #VALUE! error.

## 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 (-π/4) |

=ATAN(D1) where cell D1 contains the number 0.5. | Inverse trigonometric tangent of 0.5. | 0.463647609000806 |

=DEGREES(ATAN(0.5)) | Inverse trigonometric tangent of 0.5, converted to degrees. | 26.565051177078 |

=ATAN(-0.5)*180/PI() | Inverse trigonometric tangent of -0.5, converted to degrees. | -26.565051177078 |

=DEGREES(ATAN(TAN(RADIANS(60))) | An angle of 60° is converted to radians, its tangent is taken, then the inverse tangent of that value is calculated, and finally the result is converted back to degrees. | 60 |

## Related LibreOffice functions:

## ODF standard:

## Equivalent Excel functions:

ATAN