Wher is mistake?

Question

#include <iostream>
using namespace std;
int main(){
int a, b, c, d;
cout <<"Enter a" << endl;
cin >> a;
cout<<"Enter b"<<endl;
cin>>b;
cout<<"Enter c"<<endl;
d=sqrt(a*a+b*b+c*c);
cout<<d;
return 0;
}

Answer 1

You're missing:
#include <cmath>

You need it for the sqrt function

Answer 2

Also, there is no cin >> c

Answer 3

you missed cin>>c;
as well for sqrt you should add library <math.h>

Answer 4

All is correct except for the declaration of C and function <math.h>

Answer 5

Is the declaration of d not needed??