C++ Acos() Function

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    double x, y;

    cout << "Enter Trigonometric Ratio : ";
    cin >> x;
    cout << endl;

    y = acos(x) * (180/M_PI);

    cout << "Angle : " << y << endl;

    return 0;
}