1. The problem statement, all variables and given/known data I have a sphere and a line of radius extending from its centre to the outer surface. I would like to know the coordinates of a point on the tip of the radial line if I were to extend it beyond the surface of the sphere in a straight line. So I have the length of the radius of the sphere centred @ (0,0,0). I would like to extend the radius line outward in a straight line by a give amount. Then I would like to know the coordinates of the tip of the new extended radius line. 2. Relevant equations x^2 + y^2 + z^2 = r^2 3. The attempt at a solution (x+a)^2 + (y+b)^2 + (z+c)^2 = (r+d)^2 In the above I know what (r+d)^2 is. I need to calculate what a, b and c are.