On 2014-10-11 16:27:04 +0000, gareth said:

Relying on someone's NEC program to number crunch to
produce the answer 42 is not the same as understanding
what is going on as an aid to didactification of novices.

And having the formulas in front of you aren't much help when they
can't account for the local ground, or nearby objects.

The only way to figure it out is to do it. The math is only helpful
for spherical cows in a vacuum.