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

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


Linux: compile with gcc acos.c -o acos **-lm** -Wall   

===== C Sourcecode Example =====

<code c>
#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */

#include <math.h> /* including math library */

int main ( void ){
    double a=0.2;
    printf("acos from %f is %f\n", a, acos(a) * 90 / 3.17);
    return 0;
}
</code>

===== output =====

    user@host:~$ ./acos 
    acos from 0.200000 is 38.879955