# Ruby | CMath acos() Method

acos() method is CMath class which is used to returns the arc cosine of the given value.

Syntax: Math.acos(z)

Parameter: Here, z is the value whose arc cosine is to be calculated.

Returns: This method returns the arc cosine value of the z.

Example #1:

 `# Ruby code for acos() method ` `require ``'cmath'` ` `  `# Initialize value  ` `a = ``0``.``3584` `b = ``2` ` `  `# Printing result   ` `puts ``"acos value of a : #{CMath.acos(a)}\n\n"` `puts ``"acos value of b : #{CMath.acos(b)}\n\n"`

Output:

```acos value of a : 1.204242852965772

acos value of b : 0.0+1.3169578969248164i
```

Example #2:

 `# Ruby code for acos() method ` `require ``'cmath'` ` `  `# Initialize value  ` `a = ``0` `b = -``0``.``247` ` `  `# Printng result    ` `puts ``"acos value of a : #{CMath.acos(a)}\n\n"` `puts ``"acos value of b : #{CMath.acos(b)}\n\n"`

Output:

```acos value of a : 1.5707963267948966

acos value of b : 1.8203794286756558
```

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