There are multiple ways to find the cone missing radius based on the parameters you have. If you know the volume and height of the cone, the radius will be ΓêÜ[ (3 * v) / (╧Ç * h) ]. If you have the lateral surface area and slant height, then the radius is L / (╧Ç * s), other way is ΓêÜ(s┬▓ - h┬▓) where s is the slant height and h is the height.