Compilare: user.c: In function ‘main’: user.c:23:5: warning: implicit declaration of function ‘fabs’ [-Wimplicit-function-declaration] fprintf(fout, "%lf", fabs(arie/2.0)); ^ user.c:23:26: warning: incompatible implicit declaration of built-in function ‘fabs’ [enabled by default] fprintf(fout, "%lf", fabs(arie/2.0)); ^ user.c:14:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &n); ^ user.c:16:13: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%lf%lf", &v[i].x, &v[i].y); ^