(ii) Rectangular parallelepiped: sides a, b, c. Volume =abc. (iii) Right prism.
The parallelepiped is a particular case.
A similar procedure applies to a three-dimensional system, Thus if, 0 being the origin, OH represent any force P of the - system, the planes drawn through H parallel to the co-ordinate planes will enclose with the latter B N a parallelepiped, and it is evident H that OH is the geometric sum of 0 ~ ~----~ ~ ~---~>
(4) A parallel projection of a pair of equal and parallel straight lines, or plain surfaces, is a pair of equal and parallel straight lines, or plane surfaces; whence it follows (5) That a parallel projection of a parallelogram is a parallelogram, and (6) That a parallel projection of a parallelepiped is a parallelepiped.