View Compilation Error

0_0_30277403_12074.cpp: In function 'int main()':
0_0_30277403_12074.cpp:10:21: error: 'acos' was not declared in this scope
 #define PI acos(-1.0)
                     ^
0_0_30277403_12074.cpp:45:46: note: in expansion of macro 'PI'
   cout << fixed << setprecision(4) << left * PI << endl;
                                              ^