Form of flat Plate by which to construct any Frustum of a Cone.

Fig. 23.

Let A B C D represent the required frustum ; continue the lines A D and B C until they meet at E; then from E as centre, with the radius E C, describe the arc C H; also from E, with the radius E B, describe the arc B I; make B I equal in length to twice A G B; draw the line E I, and B C I H is the form of the plate as required.