OpenGL Camera

I wrote this, it approaches 100% accuracy as you increase the number of iterations. 4 iterations are typically required to get an acceptable answer. it does it by calculating tangent lines and where they intersect the x axis (they get closer and closer to the number's root as you keep intersecting with the x axis). im just happy as a puffer fish that the goddam thing actually seems to work accurately with only 4 iterations.

Code:

/*
	-Finds the root of x^2 - r
	-Need slope(m), need b, need curr x, need curry 
	-FIXME: add tolerance variable? i.e answer must be within TOLERANCE from real root 
*/
float	IterSqrtf(float	r, int numtries)
{
	float	m(0.0f);
	float	b(0.0f);
	float	currx=r;
	float	curry(0.0f);
	float	root(0.0f); //this is what gets returned 

	while(numtries--)
	{
		curry = (currx*currx) - r; //y1
		//Check to see if curry is < 0
		m = 2 * currx;
		b = (-m*currx)  + curry;
		root = -b / m;
		currx = root;
	}
//	trace << "tries: " << tries << "\n";
	return root;
}

EDIT: Mine is a lot slower than normal sqrt, but I'm glad that it at least works.