# How to Find Inverse of Tan or Arctan in Python

To calculate the inverse of tan in Python, we use `math.atan()` function. The inverse of tan or tangent is also called arctan or arc tangent.

A theoretical detail can be found on Wikipedia.

“Arctan of `x` can be defined as the inverse of the tangent function of `x` where `x` is a real number (x∈ℝ).” It is an angle between −π/2 and +π/2 radians (or between −90° and +90°) whose tan is `x`.

## arctan Special Values of Angles

Below is a table of some special values of angels of arctan or inverse of tan.

Some more theoretical and detailed explanation of values of `arctan`. can be found in the following table.

## `atan()` Function in Python

math.atan() function is from Standard math Library of Python Programming Language. The purpose of this function is to calculate arc tan or the inverse of tan of any given number.

## Syntax of `atan()` in Python

The syntax of `atan()` function in python is:
`math.atan( x )`

## Parameters `atan()` in Python

`x` Any valid Python number (positive or negative). This parameter is required.
Note: if the `x` parameter is not a number, `atan()` function will return an `error`.

## Python `atan()` Function Compatibility

`atan()` Function is compatible with both Python 2.x and 3.x versions.
Python 2.x – Yes
Python 3.x – Yes

## Return Value of `atan()`

`atan()` function returns a floating point number ( a value of the inverse of tan in radians).

## Python `atan()` Function Example

Output of Python `atan()` function:
` -0.19739555984988078 0.0 0.19739555984988078 0.7853981633974483 1.373400766945016 `
Note that the unit of output of `atan()` function is in radian.