yurik@yurik-pc:~$ cat test2.c
#include <stdio.h>
#include <math.h>
int main()
{
double x = M_PI;
double y = cos(x);
printf("cos(%lf) = %lf\n", x, y);
return 0;
}
yurik@yurik-pc:~$ gcc test2.c -o test -lm
yurik@yurik-pc:~$ ./test
cos(3.141593) = -1.000000
врёшь