# C++ Math acos()

This function computes the inverse cosine of a number in radian.

acos(x) = cos -1x

## Syntax

Suppose a number is x. Syntax would be:

## Parameter

x: The value whose arc cosine is to be calculated. It should be in the range[-1,1].

## Return value

Parameter Return value
-1≤x≤1 (0,∏)
x<-1 or x>1 Not a number

## Example 1

Let's see the simple example when the value of x is greater than 1.

Output:

```Value of cosine is :0.000796274
Inverse of cosine is :nan
```

In this example, acos() function calculates the inverse cosine of a number when the value of x is greater than 1.

## Example 2

Let's see the simple example when the value of x is equal to zero.

Output:

```Value of cosine is :1
Inverse of cosine is :1.5708
```

In this example, acos() function calculates the inverse cosine of a number when the value of x is equal to zero.

## Example 3

Let's see the simple example when the value x is less than -1.

Output:

```Value of cosine is :0.50046
Inverse of cosine is :nan
```

In this example, acos() function calculates the inverse cosine of a number when the value of x is less than -1.

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