View Compilation Error

0_0_39129669_12506.cpp: In function 'int main()':
0_0_39129669_12506.cpp:11:5: error: 'scanf' was not declared in this scope
   11 |     scanf("%d", &T);
      |     ^~~~~
0_0_39129669_12506.cpp:16:20: error: 'acos' was not declared in this scope
   16 |             a[i] = acos(-1) * r * r;
      |                    ^~~~
0_0_39129669_12506.cpp:21:16: error: 'fabs' was not declared in this scope
   21 |         while (fabs(R - L) >= 0.000001) {
      |                ^~~~
0_0_39129669_12506.cpp:34:9: error: 'printf' was not declared in this scope
   34 |         printf("%.4lf\n",M);
      |         ^~~~~~
0_0_39129669_12506.cpp:1:1: note: 'printf' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?
  +++ |+#include <cstdio>
    1 | using namespace std;