[schoen]

It's not nearly as flexible as bc overall, but GNU units has lots more constants built-in and also trig functions.

I checked and it has all of the ones that you mentioned, sometimes under slightly different names. I was surprised that e is defined the elementary charge rather than Euler's constant!

[majewsky]

units(1) is my go-to calculator for everything. Really nice tool. I recommend

  alias units="units --verbose"

because the verbose output is much less ambiguous.

[schoen]

Nice, thanks for the suggestion.