{{keywords>wiki library source code example reference}}
====== acos ======

<code cpp>
    double acos(double);
</code>
   calculates arccosine


===== cpp Sourcecode Example =====

<code cpp>
#include <iostream> /* including standard library */
#include <cmath> /* including math library */

using namespace std;
int main ( void ){
    double a=0.2, res=0;
    res = acos(a) * 90 / 3.17;

    //cout.setf(ios::fixed, ios::floatfield);
    cout.precision(8);

    cout << "acos from " << a << " is " << res << endl;
    return 0;
}

</code>

===== output =====

    acos from 0.2 is 38.879955