# Python atan: How to Use Math.atan() Method

Python atan() is an inbuilt method defined under the math module that is used to find the arctan of var( var is a variable that can take any number value) in radians. We need to import math module. The syntax for it would be import math; after importing, we use to call the atan() function using the static object.

## Python atan()

Python number method atan() returns the arctangent of x in radians. We can calculate the inverse of tan in Python using the math.atan() method. An inverse of tan or tangent is also called an arctan or arctangent.

### Syntax

`math.atan(var)`

### Parameters

The atan() function takes one parameter var, which takes values of any number type. Any other data type is not acceptable. If any other data type is passed as a parameter, it throws a type error.

### Return Value

It returns the arc tan value of the number in the float datatype.

See the following example.

```# app.py

import math

var = 0.36
print(math.atan(var))
```

#### Output

```python3 app.py
0.34555558058171215```

### Example programs on atan() method in Python

##### Example 1: Write a program to show the working of the atan() method in Python.
```import math
a1 = 0.36
b1 = 1
c1 = -1
d1 = -0.36

print("Value for parameter ", a1, " is ", math.atan(a1))
print("Value for parameter ", b1, " is ", math.atan(b1))
print("Value for parameter ", c1, " is ", math.atan(c1))
print("Value for parameter ", d1, " is ", math.atan(d1))
```
##### Output
```Value for parameter  0.36  is  0.3455555805817121
Value for parameter  1  is  0.7853981633974483
Value for parameter  -1  is  -0.7853981633974483
Value for parameter  -0.36  is  -0.3455555805817121
```

In this example, we have seen that by passing a valid parameter which is different for different examples, we get the desired atan() method solution, which is an arc of the tangent.

##### Example 2: Write a program to pass the value of any other datatype in the atan() function and display the output.
```import math
a1 = 'a'

print("Value for parameter ", a1, " is ", math.atan(a1))
```
##### Output
```TypeError: must be a real number, not str
```

In this example, we tried to pass a parameter which is not of real number type; hence it returned a type error stating that the number must be real.

## Conclusion

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