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The C++ Valarray::acos() function calculates the arc cosine of each element's value in a valarray and produces a valarray that contains the results.

The C++ acos() function returns the inverse cosine of an integer in radians. For each element, it makes a single call to the cmath's acos() method, which it overloads.

Syntax

Following is the syntax for C++ Valarray::acos Function −

acos (const valarray<T>& x);

Parameters

x − It is containing elements of a type for which the unary function acos is defined.

Examples

Example 1

Let's look into the following example, where we are going to use the acos() function and retrieving the output.

#include <iostream>
#include <valarray>
using namespace std;

int main() {
   valarray<double>
   varr = { 1, 0.25, 0.75, 0.5, 0 };
   valarray<double> valarraay1;
   valarraay1 = acos(varr);
   
   cout << "The acos Valarray"
      << " Value : "
      << endl;
   for (double& x : valarraay1) {
      cout << x << " ";
   }
   cout << endl;
   return 0;
}

Output

Let us compile and run the above program, this will produce the following result −

The acos Valarray Value : 
0 1.31812 0.722734 1.0472 1.5708 

Example 2

In the following example,we are going to use the acos() function and retrieving the output with comparison of original and acos Valarray.

#include <iostream>
#include <valarray>
using namespace std;

int main() {
   valarray<int> myvalarr = { 12, 143, 3, 7, 9 };
   cout << "The Orignal Valarray  : ";
   
   for (int& ele : myvalarr)
      cout << ele << " ";
   valarray<int> acosvalarray = acos(myvalarr);
   cout << "\nThe acos Valarray : ";
   
   for (int& ele : acosvalarray)
      cout << ele << " ";
   return 0;
}

Output

Let us compile and run the above program, this will produce the following result −

The Orignal Valarray  : 12 143 3 7 9 
The acos Valarray : -2147483648 -2147483648 -2147483648 -2147483648 -2147483648

Example 3

Following is the another scenario, where we are going to use the acos() function with integral type and retrieving the output in radians, degrees.

#include <iostream>
#include <cmath>
using namespace std;

int main() {
  int x = -0.75;
  double result;
  result = acos(x);
  cout << "acos(x) = " << result << " radians" << endl;
  cout << "acos(x1) = " << result*180/3.1415 << " degrees";
  return 0;
}

Output

Let us compile and run the above program, this will produce the following result −

acos(x) = 1.5708 radians
acos(x1) = 90.0027 degrees