No matching function for call to 'sqrt' in XCode 4.3

Question

I'm trying to make an SDL game for Mac using C++. I've got everything SDL-related working fine, but when I try and use the sqrt function I get the error no matching function for call to 'sqrt'. Here's my list of includes and my first function (the main() function doesn't really do anything right now):

#include <iostream>
#include <stdlib.h>
#include <SDL/SDL.h>
#include <math.h>

#include "geometry.h"

using namespace std;

void drawLine(vector2 start, vector2 end)
{
    double x = end.x - start.x;
    double y = end.y - start.y;
    double length = sqrt(x*x, y*y); // I get the error here
}

I've also tried importing with the same results. Is there anything special I have to do on Mac (Lion, XCode 4.3) to get this working?

EDIT: for completeness, geometry.h contains the definition for the vector2 struct

Answer 1

sqrt only takes one argument. You are giving it two. Perhaps you meant to do this:

double length = sqrt(x*x + y*y);

Or did you confuse sqrt with hypot?