This is the first release of a math challenge.
You have to come up with the shortest solution (9 chars or less) for a geometric function.
And the story goes like:

Pharao momo wants a square-based pyramid, where all the eight edges are of the same length 'a'.
Please support him with a formula to calculate the volume for a given side length.
Your co-workers already drew a sketch how the pyramid looks like from front-view:


Example Formula: a^3/3*sqrt(a*a)
Notation Hints: sqrt(), a^2, etc.

Enjoy!

Thanks go out to momo for the idea, Jinx for testing, paipai for a copy of EvalMath and Miles Kaufmann for writing the EvalMath class.