2) five sides are a. one side is uncertain.

Suppose that the lower right side of the graph is an uncertain edge.

The figure is movable, and the upper surface is the bottom.

The area is [(root number 3)/4] * a 2.

It is found that volume is related to height. The height is less than or equal to the opposite height.

Maximum value when equal to (root number 3)/2

The result can be obtained from the formula 1/3*sh.