The two-dimensional shape formed by slicing a rectangular prism vertically, perpendicular to the base, is a rectangle. This shape has four sides, with opposite sides being equal in length and perpendicular to each other. The two longer sides of the rectangle are the same length as the length of the rectangular prism, while the two shorter sides are the same length as the height of the prism. The area of this rectangle represents the cross-sectional area of the rectangular prism.
