Q:

What is '-1.#IND'? 

I have some code that will allow me to draw a crescent moon shape, and have extracted the values to excel to be drawn.  However in place of some numbers, there is -1.#IND in place.  Firstly if anyone could explain what this means, as Google came back with 0 links.  And secondly if there is anyway to stop it from occurring. 
There is a brief analogy of my code.  I have lots more code besides this, however that is just calculating angles. 
for(int j=0; j<=n; j++)//calculation for angles and output displayed to user
{
    Xnew2 = -j*(Y+R1)/n; //calculate x coordinate
    Ynew2 = Y*(pow(1-(pow((Xnew2/X),2)),0.5));
    if(abs(Ynew2) <= R1)
        cout<<"\n("<<Xnew2<<", "<<Ynew2<<")"<<endl;
}

MORE INFO
I'm now having the problem with this code.  
for(int i=0; i<=n; i++) //calculation for angles and output displayed to user
{                                          
    Xnew = -i*(Y+R1)/n; //calculate x coordinate
    Ynew = pow((((Y+R1)*(Y+R1)) - (Xnew*Xnew)), 0.5); //calculate y coordinate

AND 
for(int j=0; j<=n; j++)//calculation for angles and output displayed to user
{
    Xnew2 = -j*(Y+R1)/((n)+((0.00001)*(n==0))); //calculate x coordinate
    Ynew2 = Y*(pow(abs(1-(pow((Xnew2/X),2))),0.5));
    if(abs(Ynew2) <= R1)
        cout<<"\n("<<Xnew2<<", "<<Ynew2<<")"<<endl;

I am having the problem drawing the crescent moon that I cannot get the two circles to have the same starting point?  If this makes sense, I am trying to get two parts of circles to draw a crescent moon as such that they have the same start and end points.  The only user input I have to work by is the radius and chosen center point.  
If anyone has any suggestions on how to do this, it would be great, currently all I am getting more a 'half doughnut' shape, due to the circles not being connected.  

A:

#IND means an indetermined form. 
What you have there is something known as 'Not a number' or NaN for short. 
Quoting from Wikipedia, generation is done by:

Operations with a NaN as at least one operand. 
The divisions 0/0 and ±∞/±∞
The multiplications 0×±∞ and ±∞×0
The additions ∞ + (−∞), (−∞) + ∞ and equivalent subtractions
The square root of a negative number. 
The logarithm of a negative number
The inverse sine or cosine of a number that is less than −1 or greater than +1. 

You're doing at least one of those things. 
Edit:
After analyzing your code, these are 2 possibilities:

When n == 0 in the first iteration where j == 0 too, Xnew2 will be -1.#IND
When Xnew2 is greater than X, Ynew2 will be complex -> NaN

