Question 141753
the length of the diagonal is sqrt[(length)^2+(width)^2+(height)^2]


this is a serial application of the Pythagorean theorem


if you take the diagonal of any face, it is the hypotenuse of a triangle that includes two of the dimensions
__ eg. d^2=L^2+W^2


the diagonal of the box, is the hypotenuse of a triangle that includes the "face" diagonal and the 3rd dimension
__ eg. D^2=d^2+H^2 __ D^2=L^2+W^2+H^2