View Compilation Error

0_0_22590664_27075.cpp: In function 'int main()':
0_0_22590664_27075.cpp:5:48: error: 'scanf' was not declared in this scope
     while(~scanf("%lf%lf%lf%lf", &a, &b, &c, &d)) {
                                                ^
0_0_22590664_27075.cpp:6:18: error: 'dcmp' was not declared in this scope
         if(dcmp(a)==0 && dcmp(b)==0 && dcmp(c)==0 && dcmp(d)==0) {
                  ^
0_0_22590664_27075.cpp:11:45: error: 'sqrt' was not declared in this scope
         double S = 0.5*b*c*(sqrt(1-cosA*cosA));
                                             ^
0_0_22590664_27075.cpp:17:19: error: 'Pi' was not declared in this scope
         else if(2*Pi*r >= d) {
                   ^
0_0_22590664_27075.cpp:25:48: error: 'printf' was not declared in this scope
         printf("Case %d: %.2lf\n", icase++, ans);
                                                ^