Related Functions:

- ACOS Function
- ASIN Function
- TAN Function

The ATAN function returns the arctangent, or inverse tangent, of a number. The arctangent is the angle whose tangent is number. The returned angle is given in radians in the range to .

### Syntax

=ATAN(number)

#### Arguments

Argument | Description |
---|---|

number | The tangent of the angle you want |

#### Examples

A | B | C | |
---|---|---|---|

1 | Formula | Result | Notes |

2 | =ATAN(-1) | -0.785398163 | Arctangent of -1 in radians, -pi/4 |

3 | =ATAN(1) | 0.785398163 | Arctangent of 1 in radians, pi/4 |

4 | =ATAN(1)*180/PI() | 45 | Arctangent of 1 in degrees |

5 | =DEGREES(ATAN(1)) | 45 | Arctangent of 1 in degrees |

Note: If you want the angle returned by the ATAN function to be expressed in degrees, you can convert it, using the DEGREES function: =DEGREES(radians)

#### Common Function Error(s)

Problem | What went wrong |
---|---|

#VALUE! | Occurs if the supplied number argument is not recognized as a numeric value |

The arctangent is the inverse of the tangent. Therefore, for the simple right-angle triangle at right, the arctangent of the opposite side (a), divided by the adjacent side (b), is equal to the angle A. Arctangent is calculated as:

See Wikipedia for more information on Inverse Trigonometric Functions.