text: For the following code I'm getting the following error: line 15
  "Ambiguity between 'std::sqrt(double)' and 'sqrt(double)' in function main()"
  I compared the code with my friend's and they were practically identically. Yet, his got no errors. I copied and pasted his code, compiled it, and ran it. It got the same ambiguity error! The assignment itself is just a square root function and that's not the problem. The code is below:
  Code:
  #include<iostream>
  using namespace std;
  double sqrt(double x){
  double counter = 1;
  double guess = 1;
  while (counter < 20){
  guess = (guess + (x/guess))/2;
  counter = counter + 1;
  }
  return guess;
  }
  int main(void){
  double a;
  cin >> a;
  cout << sqrt(a);
  return 0;
  }