Let h and r be the height and radius of the cone.of the cone, and x be the semivertical angle of the cone.
Let be the a be the radius of the cylinder and h1 be the height of the cylinder. Then the cylinder's top surface is a circle of radius a. The height of the above the cylinder is h-h1.
Noe a and h -h1 has the relation (h-h1 )tanx = a....(1).
Also the radius of the cone and height of the cone has the relation :
h tanx = r.....(2):
From (1) and (2) we get:
We eliminate tan x between (1) and (2) by the operation (1)/(2):
(h-h1)/h = a/r.
Therefore a = (h-h1)r/h
Or radiusof the cylinder = (Height of cone - height of cylinder)(radius of cone)/height of cone.