hi, Im trying to calculate the volume of a frustum of a frustum of a cone. I understand how to calculate the volume of a frustum cone, but i need to make a frustum of the frustum cone( if that makes sense) Basically, if you imagine a frustum of a cone shaped vessel, that is partially full of liquid, im trying to calculate the volume of liquid, given;

top radius ( Rt )

bottom radius ( Rb )

height of vessel ( H )

height of fluid in vessel (measured from bottom). ( h )

I haven't done any trig for many years, and the best i could come up with was calculating the new top radius given the height of the fluid, then calculating the new volume should be easy. So far i have:

new top radius = Rb + (2 ( (H - h) * (Tan(arcTan((H / ((Rb - Rt) / 2)))))))

and the new top radius is then used to calculate the new frustum cone volume.

is there an easier way? it just seems a bit over complex to me