# R - acos() Function

The R acos() function returns arc cosine of a value. The return value will be in the range 0 through 𝜋. In special cases it returns the following:

• If the argument is NaN or its absolute value is greater than 1, then the result is NaN.

Note: aacos() is the inverse of acos().

### Syntax

```acos(x)
```

### Parameters

 `x` `Required. `Specify column to compute on.

### Return Value

Returns the arc cosine of the value.

### Example:

In the example below, acos() function is used to find out the arc cosine of the value.

```#operating on single element atomic vector
print(acos(-0.5))
print(acos(0))
print(acos(0.5))

cat("\nOperating on vector\n")
#operating on vector
v <- c(0, 0.25, 0.5)
print(acos(v))

cat("\nOperating on matrix\n")
#operating on matrix
m <- matrix(c(-1, -0.5, 0, 0.5, 1, NaN), nrow=2)
print(acos(m))

cat("\nOperating on first column of matrix\n")
#operating on first column of matrix
print(acos(m[,1]))
```

The output of the above code will be:

``` 2.094395
 1.570796
 1.047198

Operating on vector
 1.570796 1.318116 1.047198

Operating on matrix
[,1]     [,2] [,3]
[1,] 3.141593 1.570796    0
[2,] 2.094395 1.047198  NaN

Operating on first column of matrix
 3.141593 2.094395
```

❮ R Math Functions

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