Khan Academy Static

It's pretty difficult to work, mentally, with 3D objects. One way of overcoming that difficulty is in thinking about cross sections of such objects. These are 2D slices of 3D objects, and so we're back with the familiar 2D world.

3843_Ways_to_cross_section_a_cube.html

3842_Slicing_a_rectangular_pyramid.html

3844_Rotating_2D_shapes_in_3D.html