- ATAN Function
- TAN Function

The ATAN2 function returns the arctangent, or inverse tangent, of the specified x- and y-coordinates. The arctangent is the angle from the x-axis to a line containing the origin (0, 0) and a point with coordinates (x_num, y_num). The angle is given in radians between -pi and pi, excluding -pi.

### Syntax

=ATAN2(x_num,y_num)

#### Arguments

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

x_num | The x-coordinate of the point |

y_num | The y-coordinate of the point |

#### Examples

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

1 | Formula | Result | Notes |

2 | =ATAN2(1,1) | 0.785398163 | Arctangent of the point 1,1 in radians, pi/4 |

3 | =ATAN2(-1,-1) | -2.35619449 | Arctangent of the point -1,-1 in radians, -3*pi/4 |

4 | =ATAN2(-1,-1)*180/PI() | -135 | Arctangent of the point -1,-1 in degrees |

5 | =DEGREES(ATAN2(-1,-1)) | -135 | Arctangent of the point -1,-1 in degrees |

Note: If you want the angle returned by the ATAN2 function to be expressed in degrees, you can convert it, using the DEGREES function: =DEGREES(radians)

Note: A positive result represents a counterclockwise angle from the x-axis; a negative result represents a clockwise angle.

#### Common Function Error(s)

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

#VALUE! | Occurs if either of the supplied arguments are non-numeric |

#DIV/0! | Occurs if the supplied x_num and y_num arguments are both equal to 0 |

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 angle A. With coordinates (x,y) located at angle B in the triangle at right, arctangent is calculated as:

See Wikipedia for more information on Inverse Trigonometric Functions.