Given that CE= 13cm and the angle ACE is a right angle, the area of the triangle ACE is 4.5 *13/2 = 29.25cm..

The shaded area is the total area of the original paper minus the areas of the two triangular faces.

So the shadow area is13 * 8-4.5 *13/2 * 2 =13 * 8-29.25 * 2 = 45.5 square centimeters.