FRUSTUM OF A CONE
Frustum is a Latin word meaning 'piece cut off', and its plural is 'frusta'. A frustum is a portion of a solid that lie between one or two parallel planes. The frustum of cone has two circular ends with different radii. Take a right circular cone and remove a portion of it. There are many ways in which we can do this. But one particular case that we are interested in it is the removal of a smaller right circular cone by cutting the given cone by a plane parallel to its base. You must have observed that the glasses ( tumblers ) , in general, used for drinking water, are of this shape. Construction of frustum of cone Take some clay, or any other such material ( like plasticine, etc. ) and form a cone. Cut it with a knife parallel to its base. Remove the cone that is formed on one side of that plane. The part that now left is a frustum of cone. The frustum of cone has two circular ends with different radii. Let h be the height, l the slant