ROTATE FIGURE

Hello!


My problem is this:

If there is a square and it rotate around its diagonal and forms rotational body with volume V.
What will be the volume of the body that become from rotation this square around his one side???

THE RESULT IS : 3*sqrt(2)*V
Please help me !!

I` think that the first form is two cone, and the seconde is cylinder?!
But How to get this result do not know??

THANKS!!