# otp.math.acos

### acos(value)

Returns the value of inverse trigonometric function arccos.

* **Parameters:**
  **value** (int, float, [`Operation`](../../operation/root.md#onetick.py.Operation), [`Column`](../../operation/root.md#onetick.py.Column))
* **Return type:**
  [`Operation`](../../operation/root.md#onetick.py.Operation)

### Examples

```pycon
>>> data = otp.Tick(A=1)
>>> data['ACOS'] = otp.math.acos(-1).round(4)  # should return pi ~ 3.1416
>>> otp.run(data)
        Time  A    ACOS
0 2003-12-01  1  3.1416
```

otp.math.arccos() is the alias for otp.math.acos():

```pycon
>>> data = otp.Tick(A=1)
>>> data['ACOS'] = otp.math.arccos(-1).round(4)
>>> otp.run(data)
        Time  A    ACOS
0 2003-12-01  1  3.1416
```

#### SEE ALSO
[`onetick.py.math.pi()`](pi.md#onetick.py.math.pi), [`onetick.py.math.cos()`](cos.md#onetick.py.math.cos)