Compilare: user.cpp: In function ‘int main()’: user.cpp:14:12: warning: unused variable ‘x3’ [-Wunused-variable] double x3,y3; ^ user.cpp:14:15: warning: unused variable ‘y3’ [-Wunused-variable] double x3,y3; ^ user.cpp:15:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(Input,"r",stdin); ^ user.cpp:16:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(Output,"w",stdout); ^ user.cpp:17:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:19:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf %lf",&x[i],&y[i]); ^