# Python cmath - acos() Function

The Python cmath.acos() function returns arc cosine of a complex number z. It is a function on complex plane, and has two branch cuts:

• Extends right from 1 along the real axis to ∞, continuous from below.
• Extends left from -1 along the real axis to -∞, continuous from above.

Mathematically, it can be expressed as:

For any z, acos(z) = 𝜋 - acos(-z)

### Syntax

```cmath.acos(z)
```

### Parameters

 `z` `Required. `Specify the complex number.

### Return Value

Returns the complex arc cosine of z.

### Example:

In the example below, acos() function is used to find out the complex arc cosine of a given complex number.

```import cmath

z1 = 2 + 2j
z2 = 2
z3 = 2j

print("cmath.acos(z1):", cmath.acos(z1))
print("cmath.acos(z2):", cmath.acos(z2))
print("cmath.acos(z3):", cmath.acos(z3))
```

The output of the above code will be:

```cmath.acos(z1): (0.8165471820968505-1.7343245214879666j)
cmath.acos(z2): -1.3169578969248166j
cmath.acos(z3): (1.5707963267948966-1.4436354751788103j)
```

❮ Python cMath Module

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