acos in R: How to Use acos() Function in R

The arccos function is an inverse of the cos() function. It returns the angle whose cosine is a given number. Means: The angle whose cosine is 0.866 is 30 degrees. Use arccos or acos function when you know the cosine of an angle and want to know the actual angle.

acos in R

The acos() is an inbuilt mathematical R function that returns the radian arccosine of number data. To calculate the arc cosine of the specified radian value, use the acos() function in R programming. The acos() function also returns the value in radians.




The acos() function takes radian as an argument.

Return Value

The acos() function returns the arc cosine value of radian. It is a Numeric value, array, or vector.




[1] 0

Passing a pi to the acos() function

The pi is an inbuilt constant in R programming, and its value is 3.141593.

Let’s find the pi constant’s acos() value.



[1] NaN
Warning message:
In acos(pi) : NaNs produced

You can see that it returns NaN(not a number) in the output.

Let’s see another example of pi.

acos(pi / 4) 


[1] 0.6674572

Applying an acos() function to Vector

To create a Vector in R, use the c() function. But, first, let’s create a vector and pass that to the acos() function.

data <- c(-1, -0.850250, -0.507107, -0.4, 0, 0.4, 0.507107, 0.850250, 1)


[1] 3.1415927 2.5872564 2.1026212 1.9823132 1.5707963 1.1592795 1.0389715
[8] 0.5543363 0.0000000

That is it for this tutorial.

See also

R atan()

R asin()

acosh in R

asinh in R

atanh in R

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