The graph of x^2+y^2+z^2=1 is a sphere. Find two points on this sphere that are 1.5 units apart.?

I am not entirely sure if the path needs to be along the sphere but I assume not as we have not gone into great-circle distance yet. So I presume this path is the most direct possible and may travel through this sphere. I have a test with this on it Thursday night and I really need help :(