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

<code cpp>
    double atan(double);
</code>

calculates acustangens from a number

===== 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 = atan(a) * 90 / 3.17;

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

    cout << "atan from " << a << " is " << res << endl;
    return 0;
}
</code>
===== output =====
    
    atan from 0.2 is 5.6042903