Just remember folks...the flu (influenza) is an upper respiratory infection...nausea and vomiting are not symptoms of the flu . ...So many times people say they have the flu but it really is not..
Length x width x height equals volume. * * * * *. But only if the object in question is a cuboid (rectangular prism). Length*Width*Height for a sphere, for example, does not equal its volume.
Then the hypotenuse of each of those triangles is x*sqrt(2). But that hypotenuse is one of the sides of the octagon, so each side of the octagon has length x*sqrt(2) You are calling the diameter of the octagon the distance from side to side; this is the same as the length of the side of the original square.