Pyramids

two triangular pyramids with same base and height; drag any red points to adjust the shape, vertex W can be moved horizontally; drag P to examine the equal cross sections at the same level
see http://mathworld.wolfram.com/CavalierisPrinciple.html

applet created with Cabri 3D, your browser will handle the applet when you install a full or evaluated version of the software

press right mouse button and drag to freely rotate the entire figure