I did some digging. it was in this thread in a comment about bc and exponents (although I can't use a non rpn calculator on computers I just tend to type the formulas in):
https://news.ycombinator.com/item?id=5054618
a couple of replies to my comment there about exponents. specifically.
"bc is a pretty misleading calculator, without specifying rounding it thinks 2^(40/1.5) is 67108864.
It's not even close.
If you trust your finances to that, you could get in trouble. "