okay, I will call the radius of the big circle R
the little one r
and the distance between h
okay you take the sin(-1) of 1/2 the difference of R and r over hypoteuse which is the square root of that same number squared plus the height squared to get the angle of the cone on a 2 dimensional plane, then you treat that "cone" triangle as an isosceles, so you double that angle, subtract from 180, and divide by two, you now have the numbers needed to solve the equasion, that most recent number is half the angle of the 3rd angle of the triangle, and you have the distance from the first angle to the middle R, and so its just tangent of the half angle at the top of the triangle x R, now you have the full height of the cone, I assume you can do the rest.