View Compilation Error

0_0_25773459_5554.cpp: In function 'int main()':
0_0_25773459_5554.cpp:11:18: error: 'scanf' was not declared in this scope
     scanf("%d",&t);
                  ^
0_0_25773459_5554.cpp:16:29: error: 'sqrt' was not declared in this scope
         sin_k=b/sqrt(a*a+b*b);
                             ^
0_0_25773459_5554.cpp:28:27: error: 'printf' was not declared in this scope
         printf("%d\n",time);
                           ^