Reg Edwards wrote:
How about P = Square(V) / R watts

or P = Square(I) * R watts

for no phase angles.

Those are fine by me.

Just for the record, though:

V is the voltage across R, I is the current through R. This is important
when there are other components, hence possibly other values of V and I,
in the circuit. P can be average and V and I RMS; or P, V, and I can all
be functions of time -- the formulas are ok in either case. And finally,
just for the fuss-budgets, we're assuming R isn't varying with time.

Picky as this might seem, it's awfully important to make perfectly clear
just what a formula applies to and what it doesn't. Otherwise it's sure
to be misapplied in situations where it isn't valid. (Clarification
reduces the chance of misapplication from certain to only highly likely.)

Roy Lewallen, W7EL